Help with Harman Advance Cover Latch

[georgekoch3]

We've had our Harman Advance for quite awhile now, and in our yearly cleaning before the New England winter sets in, we discovered that the "Heat Exchanger Cleanout Cover Latch" had gone missing. This is an obscure part (2-00-06698B) but serves what looks to be a critical function to keep the Firebox heat exchanger covers tight and in place (don't know this for sure, but looking at the diagram and the symptoms that we had this past winter where there was an abnormal amount of ash buildup behind the ashbox, I can only assume that this shouldn't be the case).

It looks like whatever was holding it in place just sheered off:



For the life of me, I can't figure out if this is just a self-tapping screw that held it in place, or if there is a nut behind this that would need to be loosened first. I ordered the replacement part, and what it should look like is:



My question to the community as a first time poster is what would you do? I can think of a couple of options:

- Drill the broken screw and use a self tapping Grade 5 screw (or stainless steel 316 or 410?),
- Call someone in to fix it,
- Try and remove the hopper to get access to whatever is behind the screw to untighten and remove,

Any helpful suggestions would be greatly appreciated!

Cheers,
George