I am putting a new (metal) gasket where the old one was.  But I am not sure if it will seal for sure.  I would be more sure if I knew that it was machined new again.  I am afraid that the new gasket will not seal and fit into the marks that the old one made, this way not being the same effective, even if it is sealing initially.  
What is the professional reply on this?
Zoltan