I'd better check around on this one, I don't want you wrecking it. Besides, if the stem doesn't come out easily, then that is probably not the problem.

Could there have been a plug left out of the block? there are 1 or 2 pipe plugs that go in the front of the oil galley to cap that off. There often taken out when a block is checked out, and if they don't get put back in the majority of the oil goes out them, lowering the pressure. Since it is an internal leak, you'll never see it without taking the front cover off, which is what you'll probably end up doing because of your seal problem. Come to think of it, maybe excessive oil up front is related to the seal leak.