The OS LA series engines do not use bearings, instead they use bushings. That means when the bushing wears out the engine is pretty much shot...The other OS engines, the FX, AX, and FS all use bearings, the bearings can be replaced
Super Tigre is a pretty good engine..and on ground vehicles Magnum were too, although I've never flown a Magnum..I don't know if these engines use bearings or not...I assume they do.....
A remote needle valve means the valve is not on the carburator, instead it is mounted on the back plate of the engine. this allows you a little more room between your fingers and the prop when adjusting...
3 notes of caution:
1 props can and will cut long deep and continously..( I know for a fact)
2 I can't think of a trainer with a cowl..if you're a noob make sure you don't have too much airplane
3 engines under cowl require a fuel dot or a remote fueler