So long as you are reasonably careful with your measurements for the placement of the hole, you won't have any problems drilling in place.
A heavy coat of grease a moderate drill speed so you don't turn the grease into thin oil from heat and you're good to go... .
Pull the drill bit a few times as you drill, re-coat with grease (and vacuum running) is all you need to do.
You do the tapping the same way, grease it up and so on.....
Seen plenty done that way, and never a problem.
The one thing to do when you tap it is, to pull the tap after a few turns, and try the thermocouple in the hole,... it should turn in about 3-4 full turns then snug up, and that is plenty. Remember, it's a tapered hole so don't go too far with the tapping...
When you first start up the truck, just let it catch and idle for a few seconds, after that it's all good...
Bob.