I guess i need to get under there and take a closer look at it. It seems like it probably is a motor that turns a threaded rod that shortens or lengthens the rod that, in turn, moves the seat up and down. It doesn't sound like it is stuck as much as maybe the threads are no longer engaged so it's just spinning. Since I haven't had anymore response than this, I'm guessing this isn't a common/known problem with a common fix. I'll see what I can do on my own and pay someone to fix it if I can't figure it out.
The problem is, I'm 6'4" and my wife is 5'0". The seat is in the position that I like it in so it's not an issue for me. If it were, I'd have had it fixed long ago. But, I tow a travel trailer with the truck and when we go on vacation, if my wife wants to go somewhere alone, it makes it hard for her to adjust the seat so that she can comfortably see over the wheel. She can slide the seat forward, slide the power pedals towards her, and lift the front of the seat all the way up but the rear of the seat won't come up so it creates an awkward angle for her to sit.