Getting started to work on my 1974 Dart Sport. I got questions

I sounds like you might have a stout set up already. Clean it as said. Lube it (linkages ect Get it running. Oil leak Valve cover? Rear seal? Agree with flushing the fuel tank and all. Squirt a little oil in each cylinder and see if you can turn it at the crank with an 1 1/4 socket. Like said, don't go down a rabbit hole. Take your time and have some fun. Lots to learn and you'll learn it on this site for sure.