I forgot to put some on when changing my fork oil seals and the Haynes Manual directs that you do so. How crucial is it and does it warrant tearing down the forks to put it on?

 It cant come out, the axle keeps it in... soo, I think it should be ok  I didnt use any on mine and I have been riding it for 4K after I changed the seals

If you are talking about the one on the bottom of the fork 

If they are tight I wouldnt worry about it.......you will know if it loosens off,  the front end will start "Clunking"

Sledge,
Yeah, I tightened them down according to the torque specs.

Scott,
Thanks. That makes me feel a bit better.

Thanks guys