{Help Please} Head Gasket Blown?? Replacement?

[danthesk8er]

Hello,
I'm not at all a mechanic but I know how to change belts, spark plugs, and I can do a little trouble shooting. Recently I believe that my head gasket has blown. I have 1991 Plymouth Acclaim 2.5l 4cyl with about 120,000 miles on it. Recently i've had some fluctuating temperature readings, so I replaced the temperature sensor. It wasn't the temperature sensor. My symptoms now are; I have bubbles rising in the coolant reserve while the car is running and after I turn it off. My temperature gauge fluctuates more and more each day. If I let the car sit for 8-10 hours it is extremely difficult to start. The engine seems like it's trying to jump out of the car (I suspect coolant leaking into the cylinders). The last is the coolant level drops extremely fast if I let it sit for those 8-10 hours. I called a trusted local mechanic and told him the symptoms and he instantly said "blown head gasket". I could do a coolant pressure test, but I haven't yet. I believe that it is a blown head gasket like the mechanic said. I just want to make sure that it couldn't be anything else before I completely tear down the engine. If I do i have some friends that have done it before and can help me out. I also ordered the Haynes manual to help me out. If you have any suggestions they would be greatly appreciated.

(Just an FYI, at the time of the head gasket replacement I will also be replacing the water pump, thermostat, and oil and coolant change. I am buying the head gasket kit that comes will all the extra gaskets i will need and new head bolts)

Sorry about the length,
Thanks for your help

Daniel