without a puller - kinda hard to describe it, but, from the inside, with a small, angled screwdriver/prybar, hook it under the rubber so that the blade will be under the metal portion of the front of it, rest the edge on a surface while not blocking the seal, and give it a sharp rap with a hammer. no damage to anything other than maybe the rubber/spring
also, the metal strip should have been under the interior bolts, and it's tangs should have been bent up on the bolt heads as keepers/lockers so that the bolts wouldn't loosen from vibration and fall into the engine. but if you do the drill and tap for a front access, the strip won't be needed. and i'm guessing that the inside angled holes are weep holes, and used for any stray oil to drain back to the pan
