Install new crank up where no antenna has gone before??

I mounted my Winegard sideways with no air dam. I've logged about 25,000 miles since installation and have had no problems.

While generally not recommended, you can install the Sensar antenna sideways, however, you would need to provide some kind of air dam in front of antenna when laying down to prevent damage while cruising down the road as well as tree limbs and other obstructions that might grab the antenna and tear it up.
I would suggest that you are better off moving over a bit (I would call the manufacturer and ask exact where to place it) and you will be able to use the same coax from the roof (you don't need any different 12V than you have now) if you have verified that there is strong 12+V power in the coax itself.

It is no big deal to install a typical Winegard style crankup. I recently helped a friend put one in a toter and the wiring took longer than the hole drilling and mounting. You need 12volts plus the coax as the antenna is amplified. The supplied instructions were good. Go to winegard.com and look at the instruction sheet to see if you are comfortable doing it yourself.