I bought the Hidden Hitch that was recommended for the '05 MDX online (www.etrailer.com
It cost around $157, shipped, and took all of 25 minutes to install.
The only tricky part was removing the rubber hangers to lower the exhaust. But once I figured out how to remove one (by sliding it off), they all came off pretty easily.
Again, very simple. Having the hitch, for the sake of our bike rack, is fantastic.