Going to the auto shop will cost you an arm and a leg, so my advice to you is this... FIND A FRIEND WHO CAN WORK ON CARS!! I have always done my own work on cars, and have kept them running up into the 300k mileage area. The AC might just need to be charged up. You can buy a bottle of compressed Freon from autozone for about $5-$15 and you can refill the compressor yourself. Also, Overheating can be caused my several things. Your best option is to buy the Haynes-Service Manual for the 2001 Pontiac Aztec. They are available from any autozone, etc... These books guide you step by step, with pictures, and show and explain exactly how to replace or fix anything on your car. They are great! Might have to get the manual, and start checking things in order to find what is causing the overheating. Process of Elimination. It could be something as simple as a temp sensor going bad. I hope this answer has helped you. There is only so much I can try to explain to you in this answer box. Good Luck, and FIND SOMEONE WHO KNOWS CARS!!! Good Luck!