Rough Idle, won't pass smog, hasn't been driven in 6 months

Just bought a used 1996 Mazda Protege and it needs some TLC. Perhaps you could help me out with the most obvious problem that it seems to have. Whenever the car idles wether it be in N, D, R, or P, it sputters and coughs as the rpm drops to and bounces around 3-500. It doesn't quite stall but it's really close to. Additionally, the alternator belt is going and although the mechanic greased the belt it still squeals when the car starts up and occasionally when the alternator kicks up a notch. To top it all off, and what might be the actual problem, the car won't seem to pass smog and it's been mentioned that the catalytic converter might be the cause (Ive smelled the exhaust and it seems to be running a little rich). It hasn't been driven in 6 months as well, but everything else on her seems to be in good order. I don't really have a lot of money right now so the most cost effective way to address this problem would be greatly appreciated. Thanks for your time, Chris