My temp gauge stop working, is it the thermostat or temp sensor? Can I fix it? on 2006 Audi A6 Quattro

Dealer says its thermostat, but how does it make temp gauge stop working? Where are the thermostat and temp sensor located, can I fix it myself? Thank you

Asked by for the 2006 Audi A6 Quattro
try for all that info. i would believe the dealer and you will get a warranty. you can also get a 2nd opinion