timing belt back plate - water leak

hi
just got my disco its a 1996 on a P reg 300TDI.
and theres a lot of water coming from the timing belt back plate.
reading in the manual it says its a "cooling aperture gasket"
and that i should remove the whole assembly including pulleys ect and replace the gasket.
but my old man was wondering if, it would be possibly to remove a few of the bolts and slip a new gasket in then tighten everything back up again?
any ideas?

its called the p gasket the part that is leaking is not part of the timing case it is just the mounting for the power steering pump water pump and altenator
this is a common problem use gasket sealer aswell

Did this same job last week, took about 2 hours to do.
Quite straight forward, loosen the fan nut and the water and steering pump bolts BEFORE removing the drive belt.
Just be glad that it's not a 200TDI - they are a bit more complex I believe!