Never worked on a Dexta Hyd pump.
But have worked on MF 135 ones.
It would seem to me if seals are flat they should be replaced as they should have a bit of a round to them.
Also have you tried turning it in a bath of oil to see if it is pumpinmg at all.
With some ingenuity can hook it up to a drill with a belt to turn it to see if pumping, which wil confirm if seals are bad.