You have 2 hours to work on the truck and you need to understand what is keeping the engine from turning over. I hope I understand your problem correctly.
If you suspect the transmission is in gear and the clutch is holding the engine from turning, take 30 minutes to remove your drive shaft. 4 bolts at the rear yoke. Once you've removed that from the equation, the engine should turn even if the clutch is stuck/transmission is in gear. If the engine still does not turn over, take out the spark plugs and try again. If the engine still will not turn over, the cylinders are frozen. This plan will give you an idea in 2 hours.

Chris