The receiver material is soft. You can do this easily with just hand files in about 10 minutes. A chain saw file (1/8 round) works well to make the bottom radius.
Dremel milling cutters will work, but do the finishing work by hand.
A bottle of cold blueing cost about $8 and will last forever (I have a bottle I bought in 1990) - still works fine.
The gas port mod is more difficult because you need special drill bits. These bits a fragile and it is difficult to avoid breaking them if you try to free hand this at the range with a portable drill. IMO this mod isn't worth the trouble.