1) Switches are NOT built in. You will need three cables. You can mount your switch adjacent to the dish, however, which would only require two cables coming into the house. This isn't exactly preferred, and if you were to do this, at least put the switch in a waterproof enclosure. (Dish says the switches are rated for outdoor use, but...)
2) Today (or immediately after you get a SuperDish), yes, you'll need three cables from the SWITCH to your receivers - two to the 2-tuner, and one to the single-tuner. Tomorrow (meaning next year, when the DP+44 switch is available), you'll be able to feed a dual-tuner receiver with a single cable, utilizing an adapter at the receiver end to split out into the two receiver inputs.
3) Currently, no. The deal for free SuperDish is a 1 year commitment to AT50 (or better), and either locals or the HD pak. This is not to say there won't be bundles that include both an 811 and a SuperDish - but those haven't been announced yet, and no one knows the price of such a bundle.
4) It's not that tough to run conduit underneath the sidewalk - you just dig a hole on either side, then hammer the conduit through the dirt underneath the sidewalk. Beyond that, I don't know what an installer would or would not do. It sounds like your best bet is to have him mount and aim the dish, and you handle the wiring.
5) So they say...
