I found instructions on a Duramax, but what about a 6.5? I never ran out of fuel yet but figure I'd better know what to do so how do you prime a 6.5??

Turn the key on or jump the relay for the liftpump, open the bleed on the filter till the bubbles stop and it should be good. It would stall long before the IP was empty.

what about when changing injectors?

I did nothing special, just turned it over and it started.

When changing injectors, I recommend one side start truck, shut down & then do the other side, that is how I did mine.

bleeding the filter base removes air going into the pump, the remaining air in the injectors/lines clears almost immediately when the truck starts, the pump will take only a minute at idle.

The 6.5 in most cases will prime itself. It may take time, and may be crabby, but so long as there are no leaks, it will usually pull fuel up by itself. In the case of the 96 up trucks, the lift pump will cycle prior to starting as soon as the key is turned on. After injectors, just start it up...