I'll need to dig up the paperwork from when we bought it... there is over 200k miles on the odometer now, so it is probable that a clutch could the problem. I was just puzzled by still being able to shift gears with no problem engaging the transmission (no sticking or grinding...). I have a friend coming by to look at it, and this gives me something to sound reasonably competent for when they trailer it to get it to a shop... Thank you!
With 200K on the odo, the truck should already be on its second clutch, and could well be due for a third. The fact that you can move the lever from gear to gear without grinding also supports a clutch that is gone. Thje problem is that the clutch is disengaging (slipping) when it should not, which will not hinder the changing of gears. In other words, it is acting like you have the clutch depressed when in fact it is not. That is a classic sign of a clutch slipping.