[2002corolla]

as far as the the squeek is concerned it may be just one of the acc. belts. just find out where it is coming from.

now for the other prob. It may be possible that it is coolent related but I would not discount the "drip pan" for the A/C system being full and plugged thus not draining. does it have a sour/wierd smell when you have the fan blow?

for the Cat. converter to cause these probs. is not very likely, but if your check engine light is on it may very well be either the Cat. or O2 sensor ( I think you may have 2 one upstream and one downstream of the Cat. There are ways to check if the componets are good /bad. Stock Cats. typically lasts many years....It may still have some sort of warranty for the maker (can't remember if smog devices are covered for 10years) maybe something to look into. GL
Edit.....
also try to stay away from some of the aftermarket Cats. that aren't dense. as many of them dont last too long (2-4 years). but factory ones cost wayyyyyyy to much. If you were to have to take a stab at the checke engine light (without proper diagnosis) go for the cheaper of the two...o2 sensor