Mazda 626 stalls at Idle

1999 Mazda 626 4 cyl. Manual. Bought from new. Just had the intake gasket replaced as it was cracked, however after only one day the car is back to nearly stalling at idle. Mazda wanted to charge me an arm and leg for the original fix so I went to the local garage who recommended same fix for half the price. Hmmm.
I've been reading around here and it seems it could be quite a few other things - IAC valve, faulty oxygen sensors, carbon build up throughout, maybe even bad catalytic converter? I love this car but there are a few other minor problems (radio works when it feels like it, trunk is letting in water somewhere) and routine expenses coming up - tires, brakes - I don't want to sink any more cash into this when it might be used as a down payment on a new car (Mazda 8!)
Is there anything a total mechanical imbecile can do to fix / alleviate any of the problems? Or is this really only for the pros? I know they can get the codes (engine light is back on too) but shouldn't that have been revealed first time around? Appreciate any advice.