I have the nav unit in mine,so that will stay,but those garbage speakers have to go.I have the base turned up all the way,plus the loudness contour on.If the crossovers are built into the unit,I'm hosed.But if they are just crap speakers,then there's hope.I just put my pump on the drivers side, it doesn't fit perfect but its fits. Having the cargo version is good for this as there is no way for it to slide back, with the pass model you'll need some velcro and it will never move.
You'll need ford removal keys to remove the head unit or you can get creative with 4 pieces of coat hanger. Its pretty simple removal, just don't get crazy and bend the tabs out too far or it wont sit flush when you put it back in.
I somehow doubt 8" speakers will fit in the doors, if you need a guinea pig I'll gladly tackle the door panels and show everyone whats inside, its sort of my job to rip cars apart and put them back together again without extra screws. Its one of the few things I haven't taken a look at.