Noob in need of help. I am a 2 1/2 - 3 wrench mechanic out of 5 wrenches and have come across a vexing problem. My engine has 198,000 miles and cylinder 4 is misfiring so I went to swap plugs and ignition wires for general tune up/ troubleshooting to find the spark plugs literally swimming in oil. Plugs were wet above and below so what I did was clean and replace Valve Cover Gasket, Spark plugs and put in a new PCV valve. Cleared the code for misfire and ran for a day before code kicked back on and pulled the plugs again. Valve cover job fixed oil accumulating above the plugs and now the only plug wet with oil on the bottom is still cylinder 4. I need advice on where to go from here and what I can do as far as to diagnose what component/ components are failing, how to fix/ any work arounds for the meantime. Im open to engine rebuild/ engine swap with remanufactured engines being something to do but really want to get at least 1 year of driving with this engine before I need to dive into an expensive and major repair. Thank you all.