what type of Satelitte radio can be installed in to ford escape that has factory radion already?

I would get the removeable system that gets patched into your existing system. Best place to go is BestBuy or Circuit City. They have all the systems you would be interested in.

I used an older model with a tuner unit in my 2005. Had to by a controller and FM modulator and do some running of wire. Put tuner in back passenger side access panel, ran antenna through grommets in hatch and stuck under the luggage rack where it is not noticed. Any decent install no matter if you get a car dock style, or replace the stereo with one that is already equipped, will require some disassembly and ingenuity. Otherwise it will look like crap with wires all over inside the cab. I like my stuff hidden, takes longer for thieves to rip out, as one found when he ripped of my head unit in my Buick. But that was all he got.. If you use the Dock and play option, get the hardwire FM antenna splice, the wireless ones are garbage that come with vehicle dock. I couldn't find one so I made my own out of a Y splice and some F-M adapters, then I stripped the wireless antenna and made a connection to the Y. No more fuzz or station changing when going down the highway.