Idles Irradically

I have a 1986 Dodge Aries with a 2.2L engine. When I was first given this car in January of 2006 it had been sitting for 13 months. I changed/replaced the following: oil, battery, timing belt, fuel pressure regulator, fuel filter, distributor cap, distributor rotator, thermostat, spark plugs, air filter, power steering belt, and catalytic converter. I drove the car from Florida to RI (roughly 1400 miles) with very little problems. As my trip progressed I noticed that it took a little while longer to get the car to turn over when starting it. Once in RI, I started to have problems getting the car to start but once it was started it ran fine. I did some troubleshooting and replaced the coolant temperature sensor and fuel pump. It is now April and I have gotten to the point where I can barely get the car to start and it is stalling on me. I have already checked the timing belt. When I do get the car started, it idles radically and usually will get so iritic that is stalls. I have talked to a few people and researched the problem online and with a hayes service manual and have the problem down to probably a blown head gasket, an improper vacuum at the throttle body/intake manifold, a bad sensor, or a vacuum leak elsewhere in the emissions system. Most mechanics I have talked to have not been able to give me an idea of what the problem is and I have been told that it will be very expensive to find and fix the problem if I take it to a garage, which I cannot afford. The car has about 64500 miles on it and I was told by several mechanics that the engine is in really good shape when I first got it. Any idea of what the problem might be or how to narrow down the list of possible culprits?