Change the gasket NOW, dont wait for the cooling water to drain into
the combustion chamber and start corroding the piston ring seats,etc.

When you shut down, the hot combustion chamber will cool and if the
valves are closed will create a vacuum that will draw the water into
the combustion chamber .... then RUST.

While you're at it, remove the injectors and SEND or TAKE them to a
specialty automotive shop that rebuilds injectors for inspection and
rebuild if needed. Injector shops are common. - just have to search
them out.

Also be aware that the fuel nowadays has a much lower cetane number as
when this engine was designed; consider adding a 'cetane booster' to
the fuel. Cetane booster and reset injectors will remove most of the
'sooty exhaust' ... warming up the engine to full operating
temperature before applyling full throttle will also help. Nothing wll
make an engine smoke more than a cold combustion chamber.

hope this helps.