Theres a bunch of different methods people use to get rid of the liner. The key ingredient is one hot a$$ fire. Drill your intake holes first, and fire her up. Use a leaf blower or shop vac on exhaust to get it real hot. Thats what I can offer as a start.
About the ring, I love mine, because my lid is not exactly the same shape it used to be. It warped a little. So i get a GREAT seal, and when doing a cook with people around, it keeps people from peeking.
--My real name's Ty.