Margaret was pretty sure the bookshop shared a wall with the sports equipment store, and is curious to see how they've remodeled. She goes inside and takes a look around.

Clean, and very modern, and a bit bigger than it looked from the outside but not mind bendingly so. There's posters on the wall, showing science fiction and fantasy creatures. The closest to human baseline is a catgirl. Most are much farther. There's comfortable benches, and the floor is soft but doesn't seem carpeted, and there's a corner with pillows. A desk cuts across one wall, next to a door. A bored-looking girl sits behind the desk, flipping through a book. Her hair's green and spiked, and she's covered in some serious tattoos. Some of them look like they incorporate piercings. A few lights shine from her forearm - there's no real line indicating she has a latex prosthetic on holding an LED in place, but it's not impossible.

She glances up when Margaret enters, revealing eyes with little dots in them, and hums. "You been here before?" she asks, sounding distracted.

This place looks cool. Most makeover places that she's passed in malls just have pictures of nail polish bottles and closeups of eyeballs and ads implying that a slight change in skin texture is the difference between pretty and ugly.

That girl looks really cool. Her parents would say "unprofessional", but that's just a stereotype, for all they or Margaret know she went to Harvard or something. 

"I have not! Hello! So, tell me a bit about this place?" Anybody wearing LEDs as jewelry can give her thirty seconds of sales pitch; it's not like she's in that much of a hurry to get to the library.

"Rebirth Beauty Salon," the girl says. "We do makeovers. Everything from minor modifications to full-blown overhauls. Transhumanism central. We have a tattoo artist, a piercing artist, a cybernetics specialist, and a bio-modder in today. Who we have different days changes. Shop doesn't always stick around, though. Might not be here when you come back, though we can, like, give you a number and try to arrange stuff."

"That sounds awesome. Wait, are these posters examples?"

"Yup." She pops the 'p'. "Mostly boss's work."

"Wow. Definitely awesome. . . . Also probably expensive and like you have to be eighteen."

The girl shrugs. "Yeah, 's costly. Boss lets people work it off though. Taking something experimental, testing bodies, gathering stuff. Ey likes the challenge more than anything, sometimes lets weird stuff slide for cost of materials."

That gets an interested "Hmm." Even if this doesn't go anywhere, fantasizing about it seems like a reasonable use of a Saturday. "How much for a consultation?"

"Eh. Boss's weird about those. Ey doesn't charge. Thinks it's fun. You'll have to work into eir schedule..."

"Did I hear someone talking about me?" a cheery voice asks, as the door to the back opens. "Shura, you know to tell me about customers."

"You'd scare them off," the girl says, absently.

"Nonsense," the boss says, waving eir hand. Ey turns to Margaret, then. "And who do I have the pleasure of talking to? I'm Marel, the boss and head bio-modder of Rebirth."

Ey has faint scales that form a shimmering effect over eir skin, and golden eyes with a not quite human pupil, long shiny black hair, and nails that go too far up eir fingers.

That is a promising level of using one's own product. "My name's Margaret. Pleased to meet you."

"Pleasure is all mine. Are you interested in a consult?"

"I am, yes. About both biomods and cybernetics."

"Biomodification is my specialty, though I know enough about what's incompatible or synergistic with cybernetics for a basic consult."

"Fair enough. So, uh, how does this work, do I just start listing things I think would be cool or what?"

"I can provide you with a catalog of examples, if you need inspiration, but if you already have an idea what you want, that is helpful, yes. Why don't we go back to my office?"

"I have a couple ideas, but I'll definitely want to look at the catalogue. Your office sounds good." She follows em back there.

And ey provides the catalog. It's thick, with far more detail shots than the posters, and notes on anatomy and physiology - does this modification improve grip strength, are these wings usable for flight...

This is unquestionably the best book Margaret has ever read, and she has read a lot of books. She dives in. On her first pass, she has two questions: is there anything in here about stopping her aging, and what are her options for totally replacing her skin?

The book recommends talking to Marel for aging, who supplies that stopping aging is hard, especially in complex organisms! Some simple organisms are essentially immortal, but you need a process of constant renewal and a robust repair system to manage without bringing in serious magic -

Marel appears to have been nerd-sniped. Margaret is going to learn a good bit about the science of aging! That boils down to 'it's possible but expensive and needs to be built into a shape, which should be designed around 'will not die of old age''.

Skin options are easier. Scales, feathers, fur, spines, simple. Chitin you might have to rework your joints. Plant material, slightly complicated to interface with an animal body (and bark and wood require special consideration to have working joints), but also possible. Crystal and stone, difficult, and like wood require special consideration. Metal, fabric, and plastic vary depending on how organic you want your main body and how much you care about having your skin function as a sensory organ. An amorphous blob-person, difficult (the main problem seems to be neurology; the book notes that if you want a slime pet that's cheaper). Fancy options like 'lava contained within forcefields' and 'never-melting ice' are expensive but possible.

The science of aging is fascinating! She is highly in favor of designing a shape around not being the sort of thing that ages, and of being designed from the ground up in general. Her impression is that ceasing to be made of biology would help there? If she's correct on that score, the ideal surface would be metal; if biology is in fact more robust, she'll go for scales. 

The main issue is repair. Everything wears down over time. A robot can self-maintain using tools given a simple enough design, or can be maintained by nano machines serving the same function as cells, but while metal will overall last longer than organic molecules, organics are hard to beat at intelligent self-repair. A simple chassis which she must repair herself is easy, then next is biology, then after than nano machines.

Something she can repair herself sounds reassuring, at least if this place sells education as well as mods. She has ever built and maintained robots, but presumably the body she's looking at getting will be more complicated than all of them put together.

They can include a very detailed guide, yes, though they don't have classes per se.