I just repaired my Theatre of Magic dead columns using the threads I found here. I didn't drill. I bought a set of dremel glass cutting wheels. The drill is probably the way to go. If I did it again, with the dremel wheel, I'd probably go at it from the side to try to expose the tab. It doesn't take much to contact with the conductive paint. BTW, mine doesn't look like the ones above - but the fix is the same.

Dremmel wheel ($10) - https://www.amazon.com/gp/product/B016NTYAJI/ref=oh_aui_detailpage_o07_s00
Conductive paint ($15) - https://www.amazon.com/gp/product/B01M28SRH0/ref=oh_aui_detailpage_o04_s00
Ultra fine paint brush ($4) - local craft store

So basically $30. Given that I saw some used DMDs at the local pinball & arcade swap meet for $90, and the difficulty of the repair, I'm not sure I'd recommend the fix.

I'd say it's a difficulty 8/10.