How do you tell if the plenum gasket is shot? I burn roughly 1 to 1.5 qt. every oil change.

 

Look down through the throttlebody with a flashlight and see if you can see oil on the inside of the intake. Might need a mirror to look in the back of the intake to see if it is pooling up back there. There is also this TSB that you can use to further diagnose:
http://dodgeram.info/tsb/2000/09-05-00.htm