the ignition source (12v while cranking) is either a red/light green or red/black on a 99-04
or on a 96-98 tan/white or black/light green. verify with a multimeter!
the wide ban doesnt take that much current. you shouldnt need a relay to isolate it, just fuse it.
for your connection..just strip back the wire, poke a hole in the middle of it, put wire through, solder if you want, put a zip tie two inches down from the connection(to relieve stress at connection joint), then wrap your connection with "super 33" electrical tape. that stuff is the BEST!