Most everything, although I could learn valves (have done them on generators in the military), I choose to leave that to the pro aka Elskipador because it's not something I want to potentially mess up. Don't really tear down engine internals or crack cases, and the suspension stuff I let my suspension guy aka Jim @ Catalyst take care of, because, again, it's easier for him and he'll get it right, it's not something I've taken the time to study in depth enough to do myself. Studied enough to know I don't want to mess it up and just how much is going on there
Everything else is fair game. I don't trust other people touching my bikes (one bad experience was way more than enough). Granted, that means when things go wrong I pretty much only have myself to blame, but I can deal with that better than being mad that someone else didn't do what I way overpaid them for