Cylinder head gasket on SF5

[Gloubibougars]

Hello Everybody,
I'm new on the forum. I apologize if my english language is bad.
I search some information about cylinder head gasket.

First of all, I have some air pressure on cooling circuit. and i want to identify the side responsible of default.
and secondly, i search some information about cylinder head gasket changing..
If somebody have, i appreciate very much.
Thank you in advance.

Gloubiboulgars