Jim.....I've installed three of them, one on my Monaco, and silicone is actually a good product for the install. Installing the antenna is VERY simple, routing the wires is what takes some thought.
Remove the dome and seal the holes. Several will probably end up under the new antenna. Fit/place the antenna and make sure when it rises and searches it's not going to hit anything else, especially if you like to leave the Winegard batwing up for local stations.
Once you've decided, set the antenna down and make sure it's facing forward. Take a pencil and outline the antenna. Once outlined, move the antenna out of the way. Use a good bead of silicone (1/4") just inside of your pencil outline. Silicone the holes from the old antenna that will not ne used that are under the new antenna. Now, carefully set the new antenna back down over the silicone and press it into place. I don't recall if they supply any screws. I used 3/4" stainless screws and tighten them in a pattern, pulling down the sat to the roof.
Cables- You should have cables that are already there and run through the roof with a cover plate. Don't use the old cables. You should be able to feed the new cables through the old hole in the roof. There is one cable that is permanently attached to the sat (control cable) and either one or two coax leads depending on your receiver. When you attach the coax, use a wrench to tighten.
Most likely your cables will run along the roof for a couple of feet before they disappear into the coach. I use nylon cable holders with one screw to hold them down. The sat will come with a new plate to cover the cables going through the roof. I install it with silicone on the underside and then screw down.
Now that you're done installing, it's time for the Dicor. The entire edge of the sat needs to be covered, running the Dicor up and over the edge at each screw in the sat. Drop a bead of Dicor over the cable ties, completely covering them. Lastly, use the Dicor to cover the edges of the cable plate. I like to squirt a little silicone into any left over holes from the old sat and then cover with a dab of Dicor.
Many will come on and tell you that silicone is not a good product for the job. It is. If you look carefully at your exterior, all of your rub rails, windows and anything screwed to the side of your coach is capped with silicone to seal the edges. Monaco and just about every other brand uses silicone.
Once you're done on top, you just need to route your cables. The control cable and power supply plugs into the sat box. The antenna set up is done. The antenna doesn't need to be connected to your receiver to work. You could plug it in while it's sitting on the ground in your driveway and it will find and lock onto the sats.
Once you're connected to the receiver, you'll have to go through the sat setup procedure, like selecting your dish shape etc.
Good luck, the toughest part is just getting it on the roof and you have that covered!