i wouldn't bother with nomex on your grills. I put it on my performer when I was a newb.
Eventually it got so gunked and curled up that I could barely put the lid on and removing the nasty, burnt nomex was a pain in the butt.
get them back to round and do some cooking, they'll seal up.
I learned some tricks while doing a few reconditions, i'll try to write up a guide for you
on the wsm, sure if the leaks are hindering performance.
I'd personally just upgrade to the cajun bandit door before doing the nomex.