I'm not familar with your situation, but now that I re-read the question I'm wondering if it's one of those press in seals?
If so, there is a tool you might be able to use, probably called a seal puller? sort of a J shaped tool where the tip of the J hooks on one side & as you lever it back, it pulls/works the seal out of the seat.
If that's the kind of seal (and therefor tool) you have/need... you can get one pretty cheap I think (under $45,000 /forums/images/graemlins/blush.gif /forums/images/graemlins/wink.gif ) at local hardware/auto store.
I bought one when I redid my dirtbike engine & it's just been laying around since then.
If that's not it, then I'm clueless... (maybe post pics?)
Good luck