I found one oil pan bolt (M6) on the M117 engine that appears to be stripped out. It would not tighten so I removed the M6 bolt and installed it from the top side to see if any debris would come out. As I tightened the bolt from the topside and while looking up into the hole from under the car with a light, metal debris fell out.

Could a Helicoil clean up the threads? What size Helicoil will I need?

How much meat is there around it? If it's an M6 it is... small... and considering usually lots of screws on such a thing, I'd probably try to tap and jam in a slightly larger English screw, like 1/4"...

Abolutely, you can use it. But you may try just restoring the threads with a tap first. Also, if it'sca through hole, you can just use a longer bolt with a nut.

For helicoil size, you have to check the charts.

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Prost!

I went to Home Depot and purchased an M6 25 mm bolt along with a matching washer and locking nut. I gently threaded the bolt into the drain pan hole and once it stopped I held it with the wrench and then placed the washer then the lock nut and tightened it from the top on the lock nut side. Until I get a helicoil kit, it will have to do.