Connecting a HR24-100 system wirelessly to my network.

I just had my DTV installed with a HR24-100 HD receiver/DVR.  Now I realize that in order to use On Demand, I need to connect to the internet.  The DirecTV website shows that I can use a Linksys wireless internet adaptor (I only have one receiver and did not ask for whole house service) that connects to the ethernet port of my receiver.

I looked at buying the adaptor directly from DirecTV.  When I put the item in my cart, I get a pop-up informing me that I currently have 2 HD DVR receivers on my account or in my current order that can be connected to the Internet, and I am asked how many of them I want to connect to the internet.  I know I only have one physical receiver in the house, so I only need to order one adaptor, but my question is this:

Do I have to buy the adaptor lilsted on DirecTV's website, or will any wireless adaptor work? I see that Netgear has a new "Universal" adaptor (WCNE 2001) that connects to the ethernet port and costs $58 versus the almost $90 that DirecTV wants.  I am considering this one if it will work. 

Also, I know that I have to use the ethernet port on the HR24-100, but can I use a USB adaptor and a USB A to RJ45 Male connector?  Will the Ethernet port provide power for the USB adaptor?