If you have to ask, you probably need "prfessional" help. That is, installing a rear main seal is a specific operation, common to most engines. The "rope" seal in the Pontiac complicates it some, but not much.
Depending on which car you have, the engine may or may not need to "come out" to replace the seal. Doing it "in the car" is a real adventure under the best of conditions.
All the mains need to be "loosened". The rear main cap must be removed, and some "slack" created for the upper half (crank is lowered a bit). Peel the old seal out. Clean the groove (VERY important). Follow the instructions that come with the seal for install. "Forming" it is a an exercise in dexterity.
In factory blocks, we always use the GraphTite rope seal. It's light-years ahead of the old rope seals provided in most gasket sets. Most Pontiac vendors sell it.
