How hard is it to put in a new deck, with Ford's brilliant dual cd/tape player setup? Will I have to redo a lot of wiring or what?

no, get the din puller from wal mart, it's like 3 bucks, and an amp bypass install kit from crutch-field (not walmart, it won't work on our 00' GT's, I learned the hard way) and a nice head unit. You can get a din delete pocket from any ford dealership for like 20 bucks to take up the extra empty space

i changed mine in my 98 with the mach 460, was fairly simple

Guess I should have included that I don't have a Mach 460 :)

if thats the case it should only be easier.