Air Conditionig Repair--where to start?

[iufan71]

Ok,i have a 78 GMC,and it has Air on it,but its not working right now. Where do i start and what do i look for as far as figuring out what works and what my problems are? I know one of the a/c hoses has duct tape on it,so im almost positive it has a hole in it and needs to be replaced. Since there is only 3 a/c lines that i see,i thought of just replaceing those to start with. I have a 350 with auto. tranny. Any help is appreciatted.