Oily residue leaking from power head gasket

[Melvin Hatcher]

I have 1985 Evinrude XP150 and the power head and exhaust back cover plate gaskets are leaking oily residue profusely therefore, it's time for them to be replaced.
Other than that the engine runs great.
Anything special I should look for or expect to see once the engine is opened, any do's, don't do's, sealers to use, don't use?
All comments or recommendations appreciated.

Regards,

Melvin