The scope mounts to the barrel. Taking the barrel off doesn't change the scope settings. If you get other barrels, think about how you are going to put sights on them. The factory will install open sights for around $45 IIRC. Otherwise you will have to get a separate scope for each barrel.
The factory also will sell you any of the stocks they show on the guns in the catalog. Just call them at 1 (978) 632-9393. Wennig makes a stock for the NEF, as does Boyd's Gunstocks.
Hope this helps.
-Kees-