Problem with removing the a/c unit is that your serpentine belt is measured to account for the pulley on the unit and if you yank it you'll have to replace it with an idle pulley that isn't attached to anything but keeps the serpentine tensioned correctly. If no such item exists, you will be hating life trying to figure out a workaround.
I don't think you mentioned what engine it has in it, options are a 2.2 or 2.5L 4 cyl or a 3L V6--this makes a difference in trying to figure out what's up with it. For example, a transverse mounted 4 cyl is about 99% certain to have a timing belt that needs changed every 60K miles whereas a 3L V6 might very well have a timing chain that doesn't need to be replaced and it will be less likely to be transverse mounted, which changes how much your water pump is going to cost and what the failure mode would look like. I'm assuming one of the 4 cyl since the mechanic thinks it's leaking inside a cover--in which case it's pretty remarkable if you've never changed the timing belt.
