I have built numerous M-1's. I was trained by a master armorer who worked at Springfield Armory may years ago. It's not to hard but you need to see it done yourself before you try it.
If you take the plunge I also recommend Jerry Kuhnhausen's book The U.S. .30 Caliber Gas Operated Service Rifles: A Shop Manual, Volumes I & II. A treasure trove of information with awesome photos.
I have thought about this but given the price of a barreled receiver from CMP if I build one I will most likely start with on of those so all the machining is already done for me.