Its a while since I did a head gasket on a 300TDi but from memory the replacement gasket must have the same number of holes as the one you remove, the thickness of the gasket is governed by the amount the pistons protrude above the block, skiming the 300TDi head is not reccomended and does not affect the thickness of the gasket.
You should also replace the cylinder head bolts if the head has been removed in the past, I think they can be used a max of 3 times. The head is NOT just torqued down it has to be tightened in 5 stages:
Stage 1 tighten until the bolts heads just contact the head.
Stage 2 tighten to 30lbs/ft
Stage 3 angle tighten a further 60 degrees
Stage 4 angle tighten a further 60 degrees
Stage 5 (M12 x 140mm bolts only) a further 20 degrees
You can buy the degree gauge in Halfords for about £20
I hope this helps
Jim