Financial talk

I just bought an 89' Chevy Beretta. The guy told me he thought the head gaskets were bad, but wanst sure. I don't know much about cars, and would like to save some money taking it in for a test at a shop. It starts no problem, it has recently been installed with a push start ignition, the trouble comes from trying to keep it running, It sounds ok, but after a few minutes, starts to sound as if it's gonna die, unless I give it the gas and sometimes does. The coolant smells like gas inside, other than that, when I open the hood, everything looks ok, and is not leaking anything. The guy I bought it from also said that it ran great until a few months ago when his buddy ran it hard and it never ran right after that. If I really give it alot of gas, it makes kind of a whirring sound at first. I know this is a long shot, but does anyone have a clue as to what the trouble is? What I'd need to check for?..anything? Thanks.