Armed with info (and pics) from Cayman and Axxman, I went back to Circuit City. They seemed to take my word that the Explorer double DIN bracket would work, but they had none in stock, and can't order it (2004 is new style according to them, and they can only order that.)
Ordered one for 2001 Explorer from Crutchfield, will bring that to them when it arrives, and see if they will install.
I'm wondering how much hassle I'm actually saving vs. just installing myself. Can anyone advise on procedure to pull factory radio? I think I'd be fine installig the new, once I get the old one out. Thanks.