You don't need an Aluminum Plenum, just a good plastic one the is not melted between the two coolant ports and the EGR port, located on the bottom side close to where the T/B connects. Yours may or may not be damaged, I have pulled several apart and only seen 2 failed upper plenums.
For the LIM gaskets make sure to get the Aluminum style from either Felpro or AC Delco