During a DIY transmission fluid service (not the actual discussion topic, please!) one of the ~20 pan bolts broke off while removing the pan, leaving a chunk in the bolt hole. Tried a left-hand drill bit and and Easy-out extractor, but to no avail, although there is now a path/hole through the hole, it just still has some of the old bolt still in the hole that won't dislodge for some reason.

I replaced pan and re-filled fluid and watched carefully over time/driving to see if any fluid was leaking...so far so good, but it's only been a day. I've no intention of leaving it this way, but would appreciate some advice or thoughts on best path forward.

My best efforts at investigation seem to point me toward Helicoil solution. Also, is this something a numb-nutted numb-nut such as myself should attempt, or best left to a mechanic?

Thoughts?