I ordered and received the MOPAR kit from that ebay link. It includes a wiring harness. The ground wire simply taps into the sheetmetal anywhere under the headliner, and there is a long green wire that goes thru the firewall and needs to be tapped into the normal light wiring under the fuse box under the hood. It comes with instructions that show the 03-05 and the 06 truck (different fuse box designs).
I haven't installed the kit yet, just got it two days ago. Looks relatively simple, removing the headliner and drilling several holes in the roof. It comes with a full size template to find the proper light locations too.
Tony