The mirror on the passenger side is not folding in/out anymore. It happened a few times before but only for a very brief period... it's now been 5 days... so I am thinking it's dead... what have you folks done about that....

 

Replaced them.

Verify it's getting power, try the relearn. If it's not that, manual fold or $$$

 

I'm not positive, but I think the gear that drives the mirror is made of plastic. If you are particularly handy, you might be able to take it apart, make a new/repair the old, and get it working. Otherwise replacement is pretty much your only option. I haven't seen just the gear for sale anywhere, so repair isn't commonly done.

 

Power Fold Fix for $5 - Ford Powerstroke Diesel Forum