Hello!  To start off, heat is the answer.  In your case, if the
valves are fine and work, you could leave it as is.  Someone may
have already rebuilt them and you do not need to do anything.

Or, with a heat gun that emits hot air at 900 deg. C. [1652 deg. F.],
you can heat them until the adhesive, silicone or whatever, lets go,
smokes and turns to ash if necessary.

To protect the valve poppet and leather, make a metal or suitable
template that covers the surrounding wood and the open part and
hole in the plate.

I don't myself think it is a problem.

Regards,
Bernt Damm
Sydney