Yes you definitely want to use it if it checks out OK after inspection and the machinist can deck it clean, especialy since you already own it. If the decking brings the pistons to zero deck height , that's a bonus in my opinion, as long as the manifold fits afterward. Wont be able to tell what you have until you take it apart and thoroughly inspect it.
As far as the aviation sealer, stock or not I wouldn't use it to seal the heads, but that's just me. Just my two cents and opinion, others may disagree.
