This is a problem: If you can do it then you will take extreme care to do it
right. Sure a machinist can do it the machine work, but will he take the care
that you will?

Heres what I would do:

1. Get the right helicoil (or other style) kit for the drain plug size.

2. Drain the oil.

3. Put grease on the drill and/or taps while using them to catch all possible
chips. Don't drill in too deep!

4. Install the helicoil (or other).

5. WITH OUT INSTALLING THE DRAIN PLUG fill the engine with 4-5 quarts of oil to
flush out and excess chips.

6. Change the oil and filter for real.

You may want to change the oil and filter again soon after to catch any more
chips.