When I bought the tow hitch it also came with a handy instruction sheet. This is exactly what is said.
Remove cover, you will see two empty relay slots. this one goes here. That one goes there... Close cover.
and this is what is said for the hitch.
Get bolt A X 4 and install in these four holes pictures. Make sure you use thread lock (red) or some shit.
Then see capped wire on left driver side. Un cap and plug in the 7 prong tow (switch?). Click into place and place protective cover on. DONE!
This is the Armada and Titan. Dont know about them frontiers. Look into the sale brochure and see if they offer trans coolers and shit for the 2010/09. I think they just use the simple hitch...
Looked online and built me a frontier with a hitch... This is what it say's...
# Includes 7-pin connector trailer wire harness.
# Refer to your owner's manual or Nissan Towing Guide for specific towing information.
Believe me its simple. I could tow alot with the armada. If I wanted to tow like 10,000 or some shit (I dont remeber) with the armada. I had to buy some chains and some extra stuff for her. But nothing for the trans or motor from what I remeber.
Edit: Now that I remember.... I was like 15-16 years old with little automotive experience when I did that... You can do it man. Its not that hard. Just go to the dealer and ask for the relays and instruction sheet. They should give it to yah.