For your first two problems, I'm going to let someone more mechanical chime in but I can help you out with your water problem. In 1996 a TSB was released regarding the sunroof seals for wind noise and water leaks. The design of the seal in eariler models (92-95) left a gap. Mine is just shy of 3/8". There is a replacement part #12371670 which is a continous seal without a split. The dealer list is about $75 but is available from
www.gmpartsdirect.com for $44.40 plus shipping. As far as the ease of installation, I hear it is easy to install but somewhat a pain to re-align the glass. I should have my part in a couple of days and will let you know.
Also, get those drains checked! This is what mine liiked like:
To make a long story short, both of the rear drains were disconnected and the front left one was clogged. Water was pouring in from the sunfoof, along the headliner and proceded to the floor. The carpet was seriously molded and the padding was thrown away.
The third thing is that there was another TSB released regarding water leaks from the door seals. The addition of butyl rubber is GM's solution for this one. If you pull off the door seals and you see a sticky, rubbery mess clinging onto the seals than your car has already had this update.