It (the Jack Off Air antenna) is a direct replacement for the Winegard Sensar antenna. Unscrew the signal cable, pull two pins and remove the Sensar...put the Jack antenna on using the same two pins and re-attach the signal wire. That's it. When we bought our new trailer, that was the first thing that I did...take off the Sensar and install the Jack.
If you aren't getting any reception with the Sensar, you may have other issues. While the Jack is much better than the Sensar (IMHO), installing it won't correct other problems, such as a bad connectors, broken wire, etc. The Sensar that you have should pick up something, of course if you are in Moab, UT, you won't get any signals, no matter what type of antenna you have!
As for the "swap", though, it takes longer for me to get up onto the roof than it does to make the physical swap. The Jack also has an "amplifier on" LED on the antenna itself...when the amp is on, there is a red light on the antenna that glows to let you know that the antenna is powered and the amplifier is working. That way you know that the amp is on in the trailer and the antenna is receiving 12v to its own internal circuitry and that the line, at least from the wall panel to the antenna, is good. While the Winegard system has the amp light inside, it (the Sensar antenna) has no indicator to let you know whether the cable is even connected, let alone working right.