i think you need to measure a hole to find out
as for doing it
drop the exhaust manifold (oil/penatrating fluid some heat)
drop the cars oil and filter out
remove gearbox cover
remove sump (a bitch sometimes)
clean all gasket off block
seal new one on wait for it to set (gasket style dependant)
refit everything you took off
fill with oil and filter
check dipstick and for leaks regulary
ziggy