I would say just go for it, its pretty much the same leap from wanting to make a short to actually making it!!! Yes it could take a hell of a long time to complete, ive set myself a year just for principle filming (weekends, evenings basically when every my cast are free). i've never made a short but had plenty of ideas!, only done weddings and a couple of music videos, but, like you the 'Bug' is there!! if your end goal is to make money from it you'll deffo need to invest something in. Personally for me its just to say "I Made That" and have one hell of a ride while doing it. I would say that a plot/script should be your first step port of call, write it so its full length, you can always re-write parts to fit your locations/actors while still keeping your story intact.