Most rifles which have been re-barreled have also been refinished and re-assembled from mixed parts. I, therefore, do not recommend any serious attempt at restoration because some of the changes are irreversible. And any significant amount of restoration is not economical because the parts will cost more than the increase in rifle value.
In response to your second question, the finish on the receiver is somewhat rough because there was a war going on, rifles were in desperately short supply, and quantity was far more important than cosmetic quality.
Hope this helps.
J.B.