First... welcome!
Second .. no connecting wireless is not the same as having phone connection for the 622 and higher receivers. Currently the 211's can't make use of the broadband beyond what would normally be done by phone line (order / reconcile PPV, "call" home to dish, etc) but the receivers that are designed to do things like BBMP (612, 622, 722's, 922) these can use IPVOD in some form, or will be able to soon.
So.. Hooking broadband into your 622 will enable you to get additional options, including if not already, IPVOD (streaming of movies via IP / Internet Protocol - your milage may vary, as will the speed and classification of such "streaming")
Things to keep in mind ... if you already have a lot of wireless traffic, you may see additional benefit by upgrading to N devices, if that kind of upgrade is beyond what you want to pay, you might purchase an inexpensive router/bridge connect it within 10 feet of your main house router/gateway ... and then
create a second wireless network *solely for use* with the wireless bridge to your WET54G and anything you'd decide to connect to that bridge adapter.
See this picture for a basic mock up...
Again the main reason to do something like that is to allow mixed networks to keep some traffic completely isolated and non-interfering with the *other* networks.
You don't want to try and send and receive an 8 meg video stream from your dish receivers while at the same time streaming from Hulu or some other high bandwidth demand ... if on one wireless network, it would mean 2 8 meg streams in the same airwaves or a combined 16 megs of traffic ... also if in the future you add a sling adapter or slingbox to your mix you have 8 megs from the dish receiever, and 8 megs to your laptop.
As for wireless equipment .. 54G in the best situation can handle 6 to 8 megs for a single device. If you add any Wireless B devices, G will slow down.
The only benefits of buying the wireless dongle (a usb single bridge device) at Dish would be its guaranteed to work with the respective receiver, and its backwards compatible. If you don't have a wireless N router (or N-Access Point), then you're not going to get the N speed improvement.