Sure, you could always buy a DirecTV dish. Here is the latest slimline 5LNB. But why would you go buy one when they give you one for FREE??? There is alot I would not let my local D* installer do, but they are certainly capable of installing the dish, even if you need to help them pick a location or whatever.
There's a couple of reasons to buy the antenna yourself. For starters, I wanted the antenna before I was ready to move so I could set things up in the new house ahead of time. Second, I didn't want DirecTV to know I moved from NY to FL, as it can affect some of the regional sports packages and I'm a NY sports fan. Plus I was getting the East Coast Nationals as my locals and still wanted NY local news while living in FL. I pick up the FL locals OTA, so I have both markets. Last, if you do the movers package with DirecTV, you start your commitment over again. That didn't make a difference to me, but it is a reason not to get the "free install".
BTW, DirecTV doesn't care if you have a different billing address from the service location address. Besides, I get electronic bills and am set up on autopay.
Mike, the number of cables you have is fine for the switch. It's more an issue of the type and quality of the cable. I don't remember all the specs, but the recommended cable is solid-copper with 2GHz sweep. Supposedly out-of-spec cable can work, but it's not recommended.
As far as rain fade, SW Florida has a great deal of torrential rain showers, especially in summer. Surprisingly, I've had very few rain fade issues. All my signal strengths are in the high 90's. I have the Slimline AU9-S from Solid Signal that cost $99. As Steve points out, a meter is highly recommended, but that doesn't mean you can't align it without. It was just a PITA and took a few hours of running back and forth between the antenna and the TV.