Start with the model year. I think the design changed in 97. The junkyard is your likely source for replacements. My 99 and 95 service manuals are very sketchy on the mechanism itself, but it appears that both use spiral wound cable driven by a cog in the lift motor to lift the window, and it could either have slipped in the motor or be damaged in some other way. since the cable pulls upward on the window, it's possible that when your friend sat on it, it may have pulled the cable apart, ruining it completely. If the cable just slipped in the motor, the motor will likely think it's all the way up and stop before the window is up. There are no instructions in either the 95 or 99 factory manuals on adjusting these, so I am assuming that there is no routine procedure to do it. This doesn't mean it isn't possible, but to find out whether or not it can be fixed you're going to have to get in there yourself. Look at the cable and see if it appears damaged, stretched, unraveled, or whatever. If it does not, you'll have to study where it goes through the motor to see if there appears to be any way to get it back where it belongs.
The year also may determine what options there are to replace. All years came with manual windows in some trim levels, but later ones are quite rare without power. Later ones appear to be much more of a unit, with the whole regulator mechanism, including the window channels and just about everything but the glass included as one part.
