Ebay is probably your best bet (posted link below to part), and from the videos i saw it looks like the motor just simply comes out with a twist and turn like the bulbs. I bought a used cluster for the trans temp and noticed my oil moter sticks to and was gonna swap it out with my current cluster.
How to Video
Ebay Part
https://www.ebay.com/itm/P-95-02-OIL-PRESSURE-GAUGE-AIR-CORE-STEPPER-MOTOR-FOR-GM-TRUCK-SUV-CLUSTERS/271897764038?fits=Year:2002|Model:Tahoe&hash=item3f4e5ea0c6:g:sTQAAOSwpdpVeHYb&vxp=mtr
Also when time comes to replacing motors this is some helpful info from ScottyBoy
The motors in the 00-02 clusters don't have a stop position like the 03+ clusters do.
The 00-02 needles can spin freely in a complete circle if you remove that little pin that stops the needle at the end of the gauge sweep.
The ONLY thing I have seen about changing the 00-02 needles, was to get your truck up to operating temperature, and have a full tank of gas. Then take a few pictures of the gauge cluster to show where all the needles rest when the truck is idling at operating temperature on a full tank of fuel. When you go to put the needles back on, you will have to do it in the truck with the lense bezel off. Plug in the cluster with the truck idling and re-install the needles to the same place as showed in the photo that you took.
Also, if you are not changing the gauge overlay then you can put a piece of tape neat the tip of each needle, and mark where the needles rest when the truck is idling with the engine up to temperature.