They were an excellent tractor. Probably the governor needs some bearings/bushings to correct the rpm problem. Some of those parts are either very expensive, or not available any more, so that would make me a little nervous. A trip loader wouldn't be worth much in my book, maybe $500? Someone else might say more.

Beyond all that, check out the usual things like oil level, oil color. Run it long enough for it to be fully warmed up to see if anything develops once it is warm. Check the chain coupler at the front of the main transmission for excessive wear. You can change the chain without pulling the motor, but if the sprockets are worn, then your are looking at engine removal. They were a good overall tractor, so you just need to check to see how worn the whole tractor is. Look for loose steering components, especially if it is a wide front. Parts are available, but you can end up with as much in the front axle as the tractor is worth if you have to replace everything.