Anyone know how to replace lower outside top hinges compartment doors on a 2006 Tiffin Phaeton?

Most of those Tiffin lower bay doors use a top “C”/piano-style hinge, so there usually aren’t visible screws in the painted strip. The door often has to be supported and slid sideways/out of the hinge channel, or the hinge retainer/end cap has to come off first. I’d be careful those doors are heavier than they look. If in doubt, call Tiffin Parts with your VIN; they can usually tell you the exact hinge setup for a 2006 Phaeton.

Find the screws or rivets and hope you can reach them with the appropriate tool(s). 
just the first thing that comes to mind. 
Glad I could help!