First: I do not recommend making that conversion because they often use very cheap cable when wiring an RV and I really like quality RG-6... I also consider the fact that you might wish to use park cable in some parks.. (See thread on Tailgaters on the east coast..... they do not work well)
What I recommend, and did, was run a brand new RG-6 cable for the job.
Now, that said.. Here is how you do it:
IF your RV has the box of many buttons that selects several different sources for several different tv's and a VCR or DVR pull it out, on the back find the PARK CABLE lead, remove it and extend it to the sat receiver. Job done.
If you have the Winegard wall plate with the 12 volt socket, Light, Switch and Antenna connector (all 4 must be present) Or the Sensar Pro with the two digital displays, 3 buttons and a column of LED's.. Pull it,
On the wall plate it is usually the middle cable
on the sensar Pro it is labeled CABLE.
Extend it to the sat receiver and bring the COAX out on the sat receiver (If present) back to the same port you just disconnected from.