commands:
F1: play your in-game replay but dont save it
F2: save a new replay
F3: play your saved replay
go to "documents/gta sa user files" and look for "replay.rep". every time you save a new rep it will substitue the actual "replay.rep", so when landing a stunt, save a replay and change its name to something different (I recommend saving with a name you'll remember this stunt without needing to open SA to watch it).
editing: you could do it for yourself or ask someone. if you ask someone you'll need to save all the replays into somewhere like google docs or even upload them by saving a RAR archive
playing the replay: simply change the name of a replay to "replay.rep" and put into GTA SA user files (dont forget it there or you'll probably overwrite it)
anything else feel free to PM me