The most I've ever really done have been string changes and the occasional cleaning as someone above mentioned. But I recently changed string gauges on a FR equipped guitar as well as another string gauge change on a strat style bridge and it was extremely rewarding to fiddle with it until the bridges sat flush with the body when everything was tuned up.
Never done a pickup swap, but I need to. I've been jealous of my friend's Fishman's and I shouldn't have to buy another guitar just to have that sound lol.
I have another guitar here that could needs its switch fixed. The neck pickup doesn't work. In before, "why are you using the neck pickup?"
And I have quite a few volume pots that are essentially on/off switches, not tapers. I wouldn't mind eventually replacing those. My biggest hesitance is not being confident with soldering. I'ma blame it on that lol.