Owner of a 1989 K75RT and love it to the end of the trip. I've also got a F650GS Dakar, and there is no comparison: although almost 20 years older, the K is a much more pleasurable and smooth ride.
Only owner advice I have is to attend to your splines. It's not much harder than changing a tire and it's the driveshaft equivalent of oiling your chain, only you don't have to do it as frequently!
Valve clearance checking is a bit more involved on a fully faired K, the best advice I have is take your time and lots of photos when removing the fairing, and if you've got crash bars, the little rubber end bits on top come off with some persuasion and there's a bolt deep in there that is -- someone will correct me if I'm wrong -- 12 mm I think.
Oils & fluids are totally intuitive -- you don't have to take the fuel tank completely off to fill the coolant, just slide it back after popping off the c-clips at the back.
Oil and water pump rebuild (if you need to do it) is straightforward but again - take your time.
Various tubes and hoses might be due for replacement. I recently replaced the Z-tube that is like a crankcase breather up to the airbox and the bike runs smoother now.
Hmmm. . that't all that immediately comes to mind. Ride it and enjoy it!