you get the tools that align it. buy them from most motorists stores.
how do you know the valves are ok ? you can't tell unleess you remove the head , put a new cam belt on , or do a compression test.
1.8 diesels 99% of the time do damage as there is no clearance between valves and piston.
one of the aligning pins gos in a hole behind alternator to get top dead centre
second pin gos in the pump pulley at top
third pin gos in head pulley just off centre to the left.
aj mech
June 2007