Home computer repair is not brain surgery! Most computer repairs can be broken down into two specific areas, software and hardware. Now I do admit that in some peoples hand, a screwdriver can be a dangerous object. But if you can change a light bulb without shocking yourself, Id bet you could swap out a computer part. Software gets a little trickier but is still within the grasp of most computer users.
Ive been involved in computer repair in one way or another for over 25 years. The three major repairs I get called for on a weekly basis are:
Spyware/Malware Issues
Hardware failure (power supplies, hard drives, and ram usually)
Computer boot problems (lost password, toasted OS, hardware failure)
All of these can be quite a challenge depending on the value and risk of losing important data, which can be anything from tax records to photos. Any computer can be repaired; it just depends on time and budget. But not all data can be rescued. If a hard drive suffers a catastrophic hardware failure, data recovery is doubtful (unless you want spend 100s if not 1000s of dollars for special services).
So the best scenario in any home computer repair...