As far as I know, if you order the DVR through Dish directly, they will send someone out to install everything necessary and if you order from a retailer, you either have to install it yourself or pay someone to come out and do the install.
Be aware that Dish would only be able to give you the 510 with the $5 monthly DVR fee. If you want to get a 508 or 721 without this fee, you have to order it through a retailer. Since the 721 is a dual tuner receiver and not much more than a 508 and probably cheaper than a 510 from Dish, I would get a 721 from an online retailer such as Dishstore.net or Dishdepot.com and would pay an installer to come out and install everything necessary, if you don't think you can do it. Don't know how this compares to the average cost but my parents just paid $100 for having a Dish and two receivers installed in their home.
Bimmerbenz