After reading a number of posts I think I have a pretty good grasp on this but let's make sure:

Stevens .243 200 bone stock is getting a new Shilen 26" SS Varmint contour and a new stock.

Take the barreled action out of the stock and put the barrel in a vise.

Using a barrel wrench loosen and remove the barrel nut.

Thread barrel out of the action.

Apply a light coat of oil to threads of new barrel

Thread new barrel into the action, leaving it a little long.

Using a Go Gaauge set the headspace. Correctly set this should allow the bolt to close. Place a piece of Scotch tape, measured at .002, on the base of the Go Gauge, if headspace is correct the bolt will have closed on the gauge itself, but with an extra .002 added bolt will not close.

Leaving tape on Go Gauge thread barrel in and tighten barrel nut with fingers, then give it a solid rap to set it.

Re-check headspace.

If all is well go shoot.

Am I missing anything?

I plane to re-install with a new SSS recoil lug, does that affect the process any?

Any and all help appreciated.