All of the vibrations your engine is experiencing can't be good for anything.
Fixing a headgasket takes a weekend if you can do it yourself. If you can't, a shop can get it done in a day to two. My guess is that it has a large headgasket leak. If you continue to run the motor, the leak will get worse and will compromise the motor in the end, costing you more to fix it. It could be as easy as replacing the gasket and getting the head shaved for flatness, or it could be as major as a cracked head or warped engine block deck.
On the never-ending quest for better gas mileage...