Are there any individuals or shops that offer custom drone work?  I am not talking about fabricating, but more like advanced soldering skills, like adding a different camera, or receiver, or modifying a dipole to a circular antenna?

I can't see there being much, if any demand for dedicated drone repair/maintenance specialist. You might find a general electronics repair centre but they are unlikely to be able to test any of the work they do because they won't know how things are supposed to work, unless of course you are lucky enough to stumble across one who also happens to be an FPV fanatic.

You might find somewhere like Grayson Hobby will do it for you but you would need to ask and if they do, I doubt the service would be cheap.

When I read the title of the thread, I thought it's about Snow Leopard. If there's one, he and Voodoo are the forum Drone Doctors.....

LOL. If someone needed help with some physical repairs I would be quite happy to try and help out, although I'm not sure if I would want to make a full time job out of it, but again the demand isn't really there for a specialised service like that, certainly not where I live anyway.

I can see if you own a hobby shop, you can provide this kind of service. I know there is a need. But if you want to stay in this hobby, you just going to be your own doctor. It is expensive enough just to replace damaged parts, let alone adding labor to that. Might as well just buying a whole new one at that point.

There is person who lists FPV Drone Building Service UK on ebay for £29.99 +£4.99 delivery.  I have not used this service myself so judge for yourself.

https://www.ebay.co.uk/itm/FPV-Drone-Bui...OSwjgFeqpO-

There may be somebody in your own country who does the same.

rotorama does provide building a custom quad.

do troubleshooting or upgrade a quad nicely can take a lot time, a new pnp model would be less expensive often... costumm is just expensive, like a costum clothes tailor, the clothes fit perfectly but it cost a lot.

i beleive 29.99 is a stupid low price for building a quad...
seeing that racewire-leds without shrink let me feel uncofortable xD i beleive this might be not the best building quality.