The 09 Mo is not pre-wired for trailer lights. You need to either purchase the factory/OEM harness for near $200 , or you could purchase the one from the below link for $55 . I have one on order yet have not received as of yet. I read where another gentleman installed it himself and it was very straightforward. It plugs right in/between your existing tail light harness connections. UHaul may even have one of their own or obviously have access to one like this. I just wouldn't spend the $200 on the OEM.
http://www.etrailer.com/pc-VWH~118481.htm
ALSO, just so you know the hitch for the 09 Mo is extremely easy to install if you have some wrenches/sockets etc.. From the same site above you can get a $140 "Drawtite" hitch that looks really nice - as good as anything UHaul will install. Anyway, I don't know what you are paying at UHaul yet for $200 you could do it yourself very easy. Many of us have done it including myself in less than 45 minutes. The wiring harness takes about an hour given the rear panel removal/replacement etc..
Ask away if you have questions or would like pictures etc..
Good luck
Smitty