90 lumina stalls within the first ten minutes of driving?

I have a 90 lumina 3.1 four months ago during the summer it died and wouldnt start again. it seemed to be overheating. i checked the spark plugs and one of them is stripped and i wasn't able to get the money for a new head or helicoil so i could get the spark plug out. but in the winter months i got it to run and drive like normal. During the first 5 or 10 minutes the coolant light turns on and it runs really rough and will stall when you hit the gas after stoping. but after the 5 or 10 minutes the coolant light shuts off and the car runs good other than the weird idle it has which sounds like a miss but it doesn't stall. now it seems to have a small small gas leak. it has 204XXXXXX miles and shifts hard. why would it be doing this?