You don't say what engine you're running, how many miles are on the last refresh, etc, but it sounds like you have more than one problem - something causing "...smoking like crazy..." and something causing low oil pressure. The smoke is oil getting into one or more cylinders where it wasn't before, which may not be causing your pressure problem. Did all of the plugs look clean or did one (or more) have oily residue compared to the others? Your sudden drop in pressure after new stress points to a spun main bearing, cam bearing or oil pump problem. My guess (pure guess, not enough info to analyze) is that you spun a bearing, opening up clearances and dropping pressure coupled with a ring or seal letting oil get in one or more cylinders. Run it for a good easy test drive, then pull the plugs and see how they look, for a start. Listen for any new sounds on your cruise.