My tractor starts and runs until I engage the clutch, then it stalls, as soon as I push the clutch back in, it will keep running, also, when I get off the seat it continues to run, which it shouldn't, any ideas?

Clutch/brake safety switch?

Is the tractor in neutral or in gear when you let the clutch out, try neutral and tell us if it still stalls. You do have a seat safety switch issue since it should kill the engine the moment your butt comes up but it is not what's causing the clutch problem.