First time ever I had my oil changed by others, they bungled the drain plug.
2000 Chevy Silverado. It was out of town and too far away to consider
redress.

The plug is either 14mm or 9/16 inch hex head. The head seems to have a
slight taper to it. The rest of the plug is an approximate 1.5 inch
shoulder probably with a gasket. I already tried moving it by chiseling
near the edge.

I suppose my best approach at this time would be to weld on a large nut that
will fit over the hex head. I'll be using wire feed welder. Other than
disconnecting the car battery, is there any other advise before I weld?
This will be my first ever overhead weld.

Thanks,

Ivan Vegvary