There are a few hitch install threads in the forum as well as some good advice. Do you have a Summit or SRT or high Altitude? If not the OEM hitch just requires a hole to be cut in the bumper cover and trim piece installed. Check the install instructions at forum sponsor moparonlineparts.com accessory catalog. If you want trailer lights, the TIPM would need to be flashed by a dealer.
Dealers typically will not guaranty a part will fit if it doesn't show up as applicable to the VIN. Since your VIN did not have a rear tow hook, it would not show up. If you purchased the hook anyway, its yours.... no returns typically.
2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6, 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac