DirecTv- will I need a power inserter

This might be true in a home where you are trying to power 9+ tuners (4DVR plus 1) or even worse a Genie and 3 DVR's (11 tuners). You would still only need 1 coax to each box but the standard SWM setup only powers 8 tuners which would almost always be acceptable in an RV.
The poster I answered will be fine with a 2 or 4 way splitter unless for some reason he wanted to exceed 8 total tuners.