If it makes you feel any better OP, I have been a Caterpillar technician for 11 years, Im an advanced field technician now and am expected to handle any and all jobs thrown my way, usually by myself.
Anyway I had a real hell of a time with this job also. Although I did not have to resort to drilling I did end up with a brazing torch out to heat up the heads of the screws. One of them stripped so bad I had to hammer a T30 torx socket into it to remove the screw.
It took two guys to get the rest of the screw out. My brother in law would break them loose with my 18 inch 3/8 dr ratchet while from below I pushed the head of the ratchet with a PH3 bit into the screws as hard as I could.
In the end after heating, hammering, cursing, and drinking over two evenings, I was able to get the job done with all new screws.
I used Loctite 38657 High-Flex gasket maker in a thin coat over the new oring, one to help the oring stay in the groove and also to ensure it doesnt leak again during the lift of the engine. Ive linked the loctite product below. Caterpillar uses this on many of its components, from engines, transmissions, differentials, etc. Its great stuff and well worth the price. Applied correctly with hardware torqued to spec, components very rarely leak.
