Newbie Installation Question

I am trying to set up a temporary Directv installation at a lake cabin. I have an old HR-20 receiver and the dish that I took out of the ground at a buddy's house is a Slimline 3LNB SWM dish. My old configuration wasn't a SWM dish, so here are my questions:

1. I have no idea what a power inserter is but I am assuming that I have to have one with the SWM dish.

2. This old cabin formerly had cable, so can I run the coax from the dish into the cable gear to the power inserter in the house to the HR 20? Would it be better to use the power inserter prior to the cable box?

3. If I add a second receiver, are there any special hookups that I will need?

4. I tried to set up the system without the power inserter and got no satellite signal. I am assuming that would be what would happen without the inserter, correct???

Thanks for the help...