Ford Repair: 98 ford ranger lifters/rockerarms, head gasket, cushin

Question
Hi.  I asked you a question a while back (98 ranger cooling system)and you said my head gasket was blown.  I tore down and my heads were cracked, a gasket leaking and exuast valve seats were worn. After I reassembled it runs great but my rocker arms rattle a little. Rocker arms were worn about 20 thousands so I'm going to go back in and replace them. Is it common for hydralic lifters w/ rollers to go bad (160,000 miles) and do you think there worth changing while I'm in there?
  Thanks

Answer
Hello Josh, When you have intermix on coolant and oil in the engine it thins the oil out so it does not lubricate. If the engine was run any time at all the metal parts do not have that cushin of oil between them causing wear. Hope this helps Thanks Tony

Hello Josh, If you can help understand so I can clarify better and be more helpful Thanks Tony