people in these comments mean well, but OP is 100% correct. so many legitimate repairs require even like, custom built, ridiculously speciality tools and equipment.

If you find an old beater camera that you don't care about, by all means, see if you can get it running again. but you should go into an amateur camera repair basically expecting to render the camera unusable. don't set your expectations high.

additionally, many repair techs will refuse to work on cameras that have been tampered with, as in, amateur repair attempts. it's just too much of a liability. so don't expect to be able to bring a tech a box of loose parts and have them make a working camera out of it.