Okay, for anyone following this, here's an update and clarification. I didn't realize that they actually had pricing in place for taking your old shotgun and turning it into one of their works of art.
The Remington Steal package is different than their Retrofit, of which they offer Standard, Professional and Border Patrol packages.
The Remington Steal differs from the Border Patrol model as listed above in their e-mail, in that for the Border Patrol Retrofit they add upgraded 'Speed Feed' stocks, a 2 round magazine tube extension, a carry sling, and a tactical shotgun case. In addition, the Retrofit gets marked with the 'Scattergun Technologies' name on the receiver and carries their Lifetime warranty.
I spoke with John and he was very helpful. He also mentioned that since they are having such trouble getting shotguns from Remington, they are looking at discounting the price of their Retrofit package. I am now looking for an 870, new or used and will be shipping it off as soon as time permits, probably about the middle of May if all goes well. I can't recommend Scattergun Technologies enough if you're in the market for a shotgun on which your life might depend.