I think any car owner that truely is close to and loves their car would know at least a few basic mechanics to keep the car going.
In fact, I learned quite a bit about auto mechanics after I got Dryden. The fact that his 4-Tech engine is easier to work on and the fact that he's a great car helps.
When I first got a Chevy S-10 (named Slushbox) I new nothing about automotive stuff. But I learned eventually watching and helping my dad fix the truck so many times (it was a lemon, really). And then I learned a lot talking to people in car forums, and fixing a few things on Dryden. When you own a car and you want to learn, you'll learn.
So it's a good assumption that Michael would have known some basic repair skills during the time he has been with KITT. And while the KR 2K movie may have been a bit far-fetched with the technical skills of Michael (being that he was away from KITT for so long and in the boonies in a fishing boat a lot, away from technology mostly), it still could be a probability if he kept up with computer electronics on the side as a hobby "just in case" he'd ever get a chance to reunite with KITT somehow.