^^^sir listen.
there are two parts of engine assembly
upper=head
lower=block
rings,pistons,crank etc are in block.
head consists of valves,valve seals etc etc etc,gasket is the kit between head and block which prevents oil and water to mix up simply.
the problem you are facing seems a head job,when you open up the head,previous gasket becomes useless,cant be used again,so you have to get a new one.get the head done,once you take the head off,you'l see the block and condition aswell(see if there are bad rings or what)and if not,simply get the head done,get a new gasket,fix it up and u'l be good to go.
anymore question sir?