Scoobyben1

Hi all
Can anyone help I've just removed the heads of my wrx sti import as I'm rebuilding and where the valves sit the gap between them and the head gasket are some nasty pitting basically on the circular part just inside head gasket
1 will a skim rid most of the bad can I use them with small amount of pitting and have no problems
2 are they fckued and throw them away and buy new
3 if I can skim them what would be the maximum I can take of and can I make the difference up in gasket how would I work out what gasket to get as I know of 3
4 would there be any performance increase in having heads done I'm looking to get around 400bhp with the heads I've got
Please someone help