2000 Jaguar XJ8 Oil in all Spark Plug Wells - Misfiring

Engine Mechanical problem
2000 Jaguar XJ8 V8 Automatic 86k miles

I will explain problem as best as I can here, please bear with me.

Never had an oil leak problem. Regular oil changes between 3k and 5k miles. I've never noticed a problem with this vehicle and the only thing I have changed is the heater hose assembly and the fuel pump in the past 5 yrs of ownership. I have had to clean the MAF sensor due to idling issues.

After driving the car to a restaurant without any problem I was not able to start it upon leaving the restaurant. Engine would not turn over. Engine sounded like it was trying to turn over, would start and then immediately shut off. If I got the engine to turn over and kept my foot on the accelerator it would shudder while idling but when foot was removed from accelerator engine idle would slow down and engine would shut off.

I replaced the plugs. There was oil in all the cylinders. I had never seen this before and have not had a tune up recently so I dont know how long its been in there (yes, I know that's bad). I have never had an oil leak problem either. I replaced all the plugs and attempted to start the car, the same problem occurred. After changing out the plugs I hooked up an OBD code reader and got several codes for misfires in the cylinders - 4 cylinder misfires.

Does this problem sound like a valve gasket cover needs to be replaced? If I replace cover, do I replace the valve cover seals? How do I get rid of the oil in each of the plug wells? Or do I not need to deal/worry with that?

If the vehicle is not starting at all, is the valve gasket cover the least of my problems? I want to start with the cheapest repair and go from there. The new plugs I put in the engine have never been used because engine would not turn over. If I replace the gasket can I still use these plugs? Is it possible to replace the gasket, use the same new plugs and the engine could turn over?

I know I just asked a bunch of questions, but my knowledge regarding this type of stuff is pretty limited, but I would like to do the repair myself if possible. Any help would be great, thanks!