Aaron,

1) Temperature gauge: Almost for sure a bad thermostat.  This also
   could cause all of the other problems except:

3) Lose power after 5 hours: This is the infamous Vanagon problem 
   perhaps cured with a $200(?) wiring harness replacement from 
   VW, a capacitor, or re-soldering of a resistor.  I live with 
   it.  Turning the engine off and then on after a few hours of 
   driving is an easy work around.  Others can point you to an 
   archive that has lots of notes on this problem.

Mike

Michael A. Radtke  -  Z74               Voice: 602-862-4897
Bull                                      FAX:         4853
13430 N. Black Canyon Hwy.
Phoenix, AZ  85029                      Email: m.radtke@bull.com