Top goes down, goes up only so far, then stops. This is also true when in manual bypass.
Where is the hydraulic pump for the top located?

The convertible roof is not powered by a hydraulic system. It's powered by 2 electric motors (that look a bit like power window motors). It is likely that one or both of your convertible top electric motors is bad. They're DC motors so the brushes wear out over time. You should replace both. I have two 1996 Cavalier LS convertibles and I had to replace the convertible motors on both of them (once each) about 11-12 years after I bought the cars new. (I live in northern California where the weather is nice enough to put the tops up and down all year so we may be harder on our convertible top motors than other locations.) I posted instructions at the following link.
http://www.j-body.org/forums/read.php?f=11&i=125525&t=125525