Aside from my PPL knowledge of the lycoming engine for my plane (for the check ride) I don't have direct experience with working on aviation engines other than the Allison t-56-A-15 (wouldn't THAT be a fun engine on a Cozy), but I can say a bit about the 13-b or similar designed rotary engines.
They have a much higer RPM, but lower torque, you most certainly would want to go with a RGB in order to bring those rip-ems down and increase your torque. Keep in mind that the fuel cosumption would be a bit higer as well, because all three faces of the rotor are working at once. I own an RX-8 and it's crazy the power I have, but with an average of around 18-20 MPG I'd be better off with a Corvette as far as effeciency goes, even my avalanche is more fuel effecient than that.
As far as maintenance, CHECK THE OIL! Much like a preflight on any plane, check it, and if it is remotely low, add oil. A rule in the RX world is if that oil light comes on once, your'e in for an engine change.
The rotary engine itself likes turbochargers, which could provide an effeciency and performance boost on your aircraft, and it would indeed run very smoothly. If you ever wanted to do your own rebuild, you can practically take the engine out and re-rig it with a modified 5 gallon bucket to hold everythign together, the engine itself is only 3 moving parts, but there are easily twice as many seals as both the sides of the rotors and the apex seals do need addressing every once in a while.
If you are looking into one taht has been turbo charged, I can ask my friend in Wisconsin who operates a shop that ONLY deals with rotary engines if he'd be comfortable providing guidance, or building up one of his spare 13-b's for you.