I am a newbie to this but am trying to get everything back in proper order on my Audi.

About 6 months ago, my CEL came on with P0432 code for the catalytic converter. It was otherwise running alright, so of course I ignored it. The car recently began misfiring and I was forced to replace the ignition coil module. While I was at it, I replaced the spark plugs and spark plug wires. This fixed the misfires, but I still have the catalytic converter code. Does this mean the driver's side catalytic converter must be replaced or could it be triggered by something else?

I also have developed a whining sound when the car is running over the last month. I had a friend mechanic look at it and he was struggling to pin point it because it echoing through the engine compartment. He now believes it is coming from the alternator. I said he could feel significant vibration from it when he had it jacked up. Does this sound feasible?

I also believe I have an oil leak that no one has been able to pin point. A few different mechanics say that you can see where oil has sprayed inside the compartment but cannot tell exactly from where.

Is it possible these issues are related and what order should I be fixing this issues....assuming I cannot fix them all at once? Any help would greatly appreciated. Thanks.