I am going to be putting in a nice old Timberline wood insert into my masonary fireplace. The flue is 8" coming off the Timberline. I'm assuming then I have to run a 8" stainless liner all the way to the top. How do I get the 8" liner past the damper hole???? Also i have a little rust on the outside of the insert what is the best way to prep the surface prior to painting?????