94' z24 cavalier: Nice but tranny has to be put in L1 jerks then drives fine. any cheap suggestions thanks!?

I bought this car less than a week ago for under 100 from my uncle. The body is in great shape and he wanted to junk it cause of the tranny issue. I want to try to save it if at all possible but im 17 and have very little money, is there anything that I can do to help this problem that wouldn't cost over a couple hundred. Also, there may be a worn out head gasket which I have already purchased a new one for it. How hard is it to change a head gasket. Is it anything like replacing the gasket on a tractor engine? I appreciate all help THANK YOU!!!94' z24 cavalier: Nice but tranny has to be put in L1 jerks then drives fine. any cheap suggestions thanks!?try changing the transmission fluid and filter.