I have mine hooked to my Datalux. Are you sure its 3amps, mine is only 1A
I just bought a HD power extension cable, cut one of the ends off it, used yellow (12V) and black (gnd) that I extended the wires and used a DC power plug that I got from radio shack.
Center pin is +
You can use 14-16 gauge since its not much current. The fuse probably isnt necessary but certainly wouldnt hurt.