Since you mentioned backfiring and that it has been sitting (which I assume means it wasnt taken care of beforehand), I would do a valve adjustment. It's pretty damn simple on these cars. I haven't had any experience on your particular car but on mine all you have to do is pop off the valve cover, and jack up the rear end so only one wheel is in the air and the other is on the ground. By doing that you can turn the wheel that's off the ground to turn the camshaft. The only thing you'd have to buy is a valve gasket which is like $10. Only thing is dont overtighten it (which is pretty hard to do with a feeler gauge). The only tools you need are a few wrenches and a feeler gauge, and it will help alot. This probably will only make it run smoother but chances are your problem includes everything. Usually everything wears down at the same time so don't be surprised if you have to fix more than one thing.