I have an Advanced Technologies stock on an SMLE, and its about what can be expected for the price. It has never had any functioning problems, and it was a perfect fit. On the other hand, some machining marks are visible on it, and the checkering is a little low budget. It it were painted, it would look pretty sharp. It is a tough stock though, and I like it. It didn't break the budget. They also make bipods, if you want one...Versa-pods and Harris bipods are better though.
For the LER scope I would turn to Leupold, but if Burris makes one, that would be a good budget choice, and Burris scopes are more than worth the lower price. Where are you planning on getting the mounts?
As for the headspace, you can check out Brownells, and look for a guage set. There are three, GO, NO GO, and FIELD. Basically it looks like a round, and it should chamber the GO, but not the other two. I think in the military a NO GO is acceptable, but needs work when possible, and FIELD stands for field reject...scrap. Its still a good idea to have a smith look it over though.
New in wrapper rifles should be good quality, but new in wrapper means a lot of different things to different vendors. Make sure you get a good look at the rifle, and that it comes from a reputable vendor.