I did this about a year ago on my 95-850 NA without problems except some skinned parts on my hands. It took a few hours start to end. I cleaned rather than replacing the parts. My vehicle has EGR which was completely obstructed too so I removed the t.body and everything. There was a great deal of varnish-like and carbonized crud to pick out from the oil sep and the bores in the block. Reach deep into the bores to get residual pieces out that might move and re-clog the system. If I had it to do over again I would probably have replaced the oil sep box - though I think I was successful in cleaning it by soaking for an hour or so in solvent. A couple of months after doing the job I had overpressure again and found my flame trap (which you don't have I guess) clogged. I think some loosened crud made its way there. At that point I bored out the flame trap with a couple of large holes like 3-4 mm diameter (it was stuck in place). In about 10K miles I have not since had problems with overpressure. Have fun!