When I start my 91 Trooper 2.8l v.6 5pd. it want's to start driving even when in neutral, and also it will not let you shift to any gears.

What in the heck do I do?

First, make sure you have clutch fluid. My 89 has a clutch pedal adjustment. You might want to monkey with that. There is a threaded rod from the clutch pedal into the firewall. It has a tightening nut on it. Loosen the nut, turn the bolt (can't remember which way), tighten down the nut, and give it a try. I'd adjust about three or four full turns at a time. Good Luck.