I disagree, the install is very simple if it is anything like the Sirius unit. Take back the bracket and the antenna, they are both unnecessary. Go buy a nice low profile antenna from Best Buy or somewhere similar. Here's one for 40.99 with a 23' cable. I think this looks much better than the giant inside the glass antenna that Nissan sells with the Sirius kit. I don't know what comes with the XM kit though.
http://www.bestbuy.com/site/olspage.jsp?skuId=6684938&type=product&id=10837117 97612
I got my receiver and antenna from this website:
http://mynissanparts.com/pc-58-171-satellite-radio.aspx
They were fast, a lot cheaper than the Nissan website. I'm pretty sure it's a dealership selling things on the internet cheaper than they sell out the door. It came in a box with a dealership's return address on it.
-If you go for a real long one you can route it to the back of the cab. I used a 14' and routed it along the driver's side kick panel and above the drivers side wind screen. Make sure you route the antenna safely above and around the steering wheel shaft. Zip tie it off or you will have some real trouble if it tangles.
(Green arrow is the antenna wire. It is wrapped and zip tied away from shaft. This view is from the firewall looking up and out toward the driver's seat.)
-Take the little pieces of adhesive foam that came with the kit and stick them around all four corners of the receiver box. This will keep it from rattling. Attach a few pieces of the thick black double sided tape that came with the kit to the back of the receiver. Don't peel off the other side yet.
-Look under your steering wheel. On the upper right there should be a white wire harness (N-Bus) just sitting there with nothing plugged into it. That is the connection for you receiver.
(N-Bus is marked in red, on mine it was attached with one of those pop in clips, just pull that out. The OBD port is marked in blue for reference.)
-Look right above where your knees would go. You will see a flat metal plate. That is where you will stick the receiver.
(The N-Bus connector is marked in red. This view is from the firewall looking out toward the driver's seat.)
-Hook everything up before you unpeel the adhesive. Test your placement and wire clearances. If everything looks good stick it on there.
-Unlock your steering wheel and triple check that the antenna wire is not going to have any chance to interfere with the steering wheel shaft.
(Antenna is marked in green, the purple arrow is pointing to the upper part of the brake pedal.)
-Turn on your car. Call, or go online and they will walk you through the activation. (Sirius did, I assume XM will too)
Edit: Stopped raining, here are the pics. I'll get a few pictures of my install and post them here. It's a very easy install. If it takes you 45 minutes including beer breaks I would be surprised. Good luck.