The Surgeon is easy to assemble, so long as you have the right tools.
I have built a couple of rifles on Surgeon S/A and am ongoing a build on a XL at the moment.
You must remember that the action comes in the white and will need coating of some kind before final assembly of componants (parkerising, blueing, duracoat, krylon etc etc etc)
Once its coated, assemble componant parts, but not before.
My guess is you may be having the barrel assembled by gunsmith and completing the rest of the build yourself?
Anyway, the bolt stop will be in a small bag with the relevant componants - spring, stop and roll pin.
My advice if you do it yourself is insert pin from underneath, then if you slip with your punch and hammer the ding wont be seen.
Here is one I made earlier: