I made a vulcan writeup several years ago at: http://nerfhaven.com...ulcan-overhaul/
Time has proved that the electrical work was way, way sub-par. If you attempt a mod, do NOT use trustfire batteries. Use a real lipo and redo all the wiring in heavier gauge wire.
That said, my writeup references and links Split's original writeup, and is maybe good for a reference of how you can remove the AR and/or do a spring swap. Its pretty well impossible to make a vulcan not HvZ legal as far as power is concerned. Upping the voltage will improve your rate of fire tremendously, which is the advantage of a vulcan in an HvZ setting, which some HvZ Moderators may take issue with. With crap wiring and crap batteries, I was getting a rate of fire in the neighborhood of 600 rounds per minute.
I will say that it may not be wise to crack into a vulcan as your first mod. Its a relatively complicated blaster in terms of the mechanics, and if you've never performed a mod before, all the pieces may become overwhelming.