go over your records.
any headwork done?
timing chain been replaced before?
assuming these things have not been done before,
pull both heads,and have them checked for "flatness"
replace valve seals,check springs etc etc (whatever the machine shop suggests,providing they are GOOD!)
or buy already rebuilt heads.
also replace timing chain and "Rails"
inspect cam and lifters for wear,and replace if needed.
REPLACE the plastic oiler pieces that oil the cam!
(do this anyway!)
you will need a head gasket kit
(one for each side)
"Partshop" on this site is a good place to get these parts!
I think thats the majority of what SHOULD be done.
doing this while you are in there saves lots of Labor $$ in the future.