So this question probably needs some context.  My game's setting is similar to dying earth where all magic is technology, and though your average person doesn't get that, wizards and such do get that and understand its tech.  So "arcana" = "technology" in some form or another. My campaign is also set on far-future earth.

In a previous campaign, my PCs discovered a gene splicer.  It took them a while to figure out how to use it but when they did they had a lot of fun with it (troll regen anyone?).  In terms of how it worked, I stole it directly from the Gardens of Ynn.  So the PCs had to experiment with it to get it working, ie, it became a toy for them to play with.

I am looking for some similar inspiration (or something I can outright steal) from another source.  My initial idea is to just make it hard to get to (it's level 10 of a dungeon) but once they get it, automated machinery there can do the job.  But if I could add an interactive/discovery piece to the actual cybernetics process, that would be great.  Gene splicer from Ynn is a perfect example (but don't want to reuse that for cybernetics).

Thanks in advance.

A cybernetic skill implanter? Something that inserts a device into a pc that's basically a plug for a skill chip to be implanted into? So the player can have a skill implanted in him?

A biotech hive inserted in the pc that grows and hosts tiny symbiots, think real hydra, that help heal the player abd fight diseases?

List of cybernetics I have. Install process I have. It's more a process or "puzzle" to figure out that process I am after.  For example, in Ynn the PCs have to to press buttons in a certain order to get a result. Pressing the wrong button can be catastrophic.

Hate to suggest it... But sounds alot like D20m Gamma World from White Wolf.
Next to rampant nanotech there was extensive biotech which allowed for easy grafting of widgets onto people or even larger scale biomodding. Combined with nanotech things could go south really fast. Sexually transmitted PC? Yep, that was a thing. Copying onto a person and completely overwriting them. Monsters that were originally normal animals infested with a bioweapon that totally transformed them was another.

There were several examples in the books. But at the end of the day it was whatever you wanted it to be for a campaign.

So the question then is how extensive is it and are there any drawbacks?
Example: In FREE Lancers one of the example characters has a helmet that allows him to upload into his brain any skill. Problem was he starts hallucunating that he is that person. A more refined version was given to another agent. But she became addicted to the system and so paranoid that she went rogue.

Not so wild as that.  The implants are high-tech so would not be obvious unless the "customer" asks for them to be obvious.  Here is my first cut:

https://www.worldanvil.com/w/the-ninth-world-solomani/a/92-legio-cybernetica-lab-article?preview=true