Welcome aboard macsailor. I'll reply since I am definitely an 'old voomer'.
Point 1 was about installation. All the satellite companies sub-contract their installations, so in that respect--Voom is no different than D* or E*. Once the order is placed, we are all subject to the availability of the installer. You've got yours all set for Sunday, and we'll be pulling for you. Best of luck!!
Point 2 was on OTA. You mentioned speaking to a tech, but that was probably a CSR. They are not the definitive authority on quoting the number of OTA channels that you will get. Best advice is to let the installer do their thing. The new software has OTA scanning, which automates part of the installation for OTA. Go to antennaweb.org and print the digital channel list for your zip code. Have that ready on Sunday, and see what channels you end up with. If there is a problem after installation, deal with it at that time. You may need to re-orient your antenna or get a bigger one, but you won't know until after it's installed. Generally, you want your OTA to be as high as possible, with a clear line of sight to the broadcast source.
Point 3 was your new Sammy in your new house. Upon installation, you may not have the latest software installed on the set top box, but it will update through the satellite. Usually on the first night, but it may take up to 3 days before an update.
Now here is my best advice....stay in touch. This forum is a great place to get information and to troubleshoot anything that's wrong. You get real-time answers from people who know what they are talking about. Here in the Colorado thread, we have one of the most knowledgeable guys on the whole forum in Sat4me. GEBrown is another good guy who seems to be pretty 'up' on his satellite knowledge.
It is easier and faster to post here, and you usually get answers that are better than what you would get from customer service, so use the forum. Again--welcome, and keep in touch.