Don't be afraid to dive in to this bike if it does break. You'd be amazed at how simple these things are. I've seen toasters that are more complicated than these bikes. Cavemen must've designed them shortly after inventing the wheel. I timed myself swapping those heads today: I got the left piston off in 5 minutes.
The inside of the gearbox is basically off-limits to a guy in his own garage. Also, you're not going to be able to work on your heads. That's it. Anything else on the bike you can take care of yourself with basic hand tools and ADVRider. Actually, you can fix gearboxes and heads too. Simply swap them out for another one that you get on ibmwr.org or ebay.
I went by a buddy's house tonight to pull those heads off his r80. We put some r65 heads back on it. When we went to bolt up the heads we found that the pushrods were 1/2" too long
We rooted around in some boxes and found some shorter pushrods and they fit perfectly. Swapped the heads and exhaust in maybe 45 minutes and had time for 2 beers
The bike can take credit for that though, not us. We're both poor mechanics and we never work sober.