Just to make sure you read that right, its just a 1/8 to 1/4" that you rotate the seal, not a 1/4 rotation. This is just so that the seal ends aren't meeting in the exact spot where the end cap surface is. If you put a dab of sealant on the end cap surface you should be fine, but like mentioned above, if you don't have the pan on, I'd go ahead a pull the cap back off, clean it up, rotate the seal slightly and put it back together. Should only take about an hour to do that verses a whole day to do it over.
The key to no leaks is letting the sealent on the end cap try completely and thoroughly before running again. I let mine sit for over 24 hrs before putting the pan back on to make sure it got all the air it could to cure. Also make sure the pan gasket is very clean and the pan surfaces/black is very clean of any oil and it should not leak, even with the dreaded rubber pan gasket that everyone claims leaks, I didn't have a problem.
Tie the pan gasket to the pan with fine string, once you get the pan in place with a few bolts, cut the string at the various points and tighten up the pan then, this way the gasket stays put when putting the pan up and keeps any oil from getting on it. No sealant on pan gasket, just a dab of it where the front cover meets the block and where the end cap surface meets the block.