Switching to Dish - Best way to get equipment?

I'm wanting to switch from DirecTV to Dish (ViP-622). However, my house has a lot of trees around it. I have no problem seeing the D* birds (98/100 signal), but from what I can gather, the Dish birds are going to be about 7-degrees lower in elevation. This may present a problem with the treeline. I just can't be sure. I had to mount the D* dish on the chimney, but I'm not sure my somewhat unstable chimney will handle the load of the larger dish. The small 18" D* dish hasn't given me any problems for 6 years.

So, I called Dish first, and the CSR said that an installer would have to install the dish. However, they said I would be charged for the 622 even if the installer is unable to get a signal from the sats. Umm, no thanks!

So, I called the local Dish dealer. This wasn't fun. First, the guy told me that I needed the 625, not the 622. When I repeated that I wanted the HD service, he said the 625 does HD. Uh, I don't think that's correct. He then argued with me about how many receivers I wanted installed. When I finally got him to understand what I needed, he said they would do a site survey before I paid for anything. Nice. He said he was on his way, but that was 3 days ago. I called back, but no response.

I'm already getting a bad taste in my mouth for Dish. Why is this so difficult?

Can anyone recommend the best way to get Dish service, but be able to have the installer do a site survey first before I pay for anything? The trees are in my neighbor's yard, so there's nothing I can do about them.