If it's the same pattern as the output seal (and I've no idea if it is - I've done two output seals but never an input), you could try 'self tapper' technique:
Carefully drill two opposed holes in the steel facing of the seal, part way screw in some small self tappers (try the drill / self tappers out on some scrap first), grab them with long nose pliers and carefully pull the seal out. You'll have to find some suitable tubing or a big deep socket to drift the new seal in.
it's a loooong tunnel - So two (very) long right angled picks - insert down the long tunnel, hook into seal along the inner edge, twist picks so right angle is under the seal and pull out.