I know that in order to access the 3 rear plugs on my 96 gtp, i have to tak the manifold off and plenum etc.....but is there any easier way, or tips anyone has...or even really good detailed instructions??????any help is greatly appreciated thanks!

A repair manual is required here. For $15, they are a DIY'ers best friend. The upper plenum bolts should be torqued in a specific sequence, to a specified torque value, and the repair manual will give you this info, as well as a bunch of other info about other systems of the car.