OmarR did one.
http://z71tahoe-suburban.com/iboard/index.php?showtopic=19909
It is about adding a gauge, but it applies to changing the motors too.
Change them all btw, not just 1.
that's what I used to take mine aprt and replace the motors.
Exception is in needle pointing: turn them counter clockwise until the bottom out.
Lay a strip of tape to mark where the needles are.
with your fingers, turn the shafts counter clockwise on the new motors after install.
When reinstalling the needles install them slightly 'higher' on the gauge, then turn counter -clockwise to match up with tape mark.
they will now point to 0 first time instead of having to remove and turn and reinstall each one individually.