You can easily remove the antenna by udoing the 2 screws on the base and pulling it out. There is a connection at the radio, but I don't know if there is another one. In case there is just the one, undo it first so you can draw the whole cable out. If there is another somewhere along the cable, maybe just puling will undo it. Maybe there is one at the bottom of the antenna, I never looked.
Then get a blanking cover for the hole. It is found on Escorts with no radio, so you could check the boneyard or the dealer. How much could it cost?
Then get a power antenna from walmart or something. It is controlled by the power antenna lead on the head unit. If you are about to buy a head unit, then get one that has a power antenna lead. Most do these days.
The antenna needs a constant 12V and the control lead. It's cool because the antenna goes down when you switch to CD.
For mounting, they come with a variety of bases to accomodate most deck profiles and angles, but you still need to be somewhat horizontal, unless you're prepared to do major bodywork for a nice recessed hole in the side of the body, so pick the top side of a front or rear fender. Rear seems better here.
You also need room underneath for the guts of the antenna, so some trimming and re fabbing of the interior panel might be needed.