It should be no problem to connect a dish to the livingroom receiver, but unless you are using a Genie, you need another line for each receiver. The way DirecTV works when you want to use more than one receiver with a dish, is to insert a multiswitch between the dishes and the receivers. This looks like a big signal splitter, but is much more. If you use the slimline SWM system, a single RG6 cable will provide signal to both tuners inside your receiver. With the older system, a separate cable is required for each tuner.
Lots of people have created home made systems with a dish on a tripod. Most use the round SD dish (no high def) since it is far easier to aim. You can buy these dishes on ebay and lots of outlets for tripods. You can even get the high def slimline dishes. Just be prepared for more critical aiming. You can also get a multiswitch which you can mount in your UDC. You still have to run RG6 to the bedroom from the UDC no matter which option you choose.
A more expensive, but far nicer solution is to get a Trav'ler dish mounted on the trailer's roof. We have that and it is fully automatic. We get to a site, turn on the Trav'ler and it aims itself. Since it is a slimline, SWM setup, each receiver (you can have up to 4) has both tuners working (record one show, watch another, etc.). We got a good deal from Camping World. Well, not initially. We found the dish $400 less than CW's price. Showed it to CW and after some hassle (involving a post to the CW/Sam's Club forum and a reply from CW CEO), they matched Amazon's price and installed for $39. The install flat rate has gone up a bit, but it was a great deal.
If you want to do it yourself with two receivers with both tuners working, you need to build a SWM system. It isn't that hard to do, ebay has the stuff. But you you should expect to spend considerable time aiming at each stop.
