What parts other than 4-1 header and CAT are required to install properly? Is a new header gasket needed? Or can I use the stock one? Also, what needs to be done for the other O2 sensor? just drill a hole and use a gromet? Or does it have to be drilled and tapped...(what size)

I want to know all b4 Saturday...so when I get there...he doesn't try the old "well we needed to do this and this and this and now your total is 300.00 rather than $150.00


thanks