In the end I opted for the Mercedes RTV which is a lot easier to get than Peramtex. Here, the Merc stuff, costs 28€ (about $30).

I did the reapir over the weekend, leaving it 48 hours to dry before completely tightening (it's pretty cold here at the moment), and reused the same bolts that were already on (Mercedes wouldn't sell me the bolts, only the cover with bolts for $300).

I did both sides in the end, hopefully everything looks ok, but only time will tell. I still got a bit of burning smell (first time I drove the car today), but that could be caused by leftovers from before (not had chance to clean the engine yet, only cleaned the part that I worked on).

Thanks again for all the help.