for better life of the bottom bracket bearings, it is suggested to have that area of the frame "faced", with a special bike shop tool that makes sure that both sides are exactly parrallel and that there is not any paint "bumps" left.
given that you are starting from a bare frame, its worth it to get this done, or at least verified by an experienced mechanic at a good bike shop that knows what they are doing.
re putting some sort of frame saver product inside the frame, I agree that it is worth doing considering you are starting from scratch, from a bare frame. I bought a used bike last year and dismantled it, and while it was a bare frame, I did this procedure--I figured why not, it will be the only time the frame is all apart.
of course, if you didnt do it, its not the end of the world.
I do think its worth getting the bb bottom bracket shell part of the frame checked , for longest bearing life with outboard bearings. This is only from what I have read, I dont have lots of experience with outboard bb's, but it is probably worth at least asking an experienced mechanic that you know is good, about this aspect.