C4 tranny help....please.

i have a 64 falcon w/a 289 ci. its currentl mated to a C6 from an 83 f350. too big. obviously. i recently acquired a C4 from a guy, and it looks to be in good condition, but i dont know anything about transmissions. im sure it needs to be rebuilt. can i just buy a rebuild kit and do it myself? or should i just let pros take care of it for me? i want to learn more about trannys so any info helps...thanks folks. what are signs to llok for on the tranny to make sure its a C4? he told me it is and because it was free i didnt ask questions. okay thanks.