Yeah man I hear ya. Money's been tight this way, too. I can't remember the last time I bought something for the truck. Yeah double-din is the large radio size and single din is essentially half, with the small pocket below like you mentioned. The GPS was pretty simple. It has a little receiver about the size of a box of matches with a small magnetic plate that it sticks to. You mount the place somewhere, run the wire, and stick the receiver on it. I put mine in the far corner behind my Gryphon. The GPS on the unit is amazing, though.
Wow 

God I love the sound of those things