This spark plug was covered in oil (on the porcelain part), does anyone have an idea as to what might have caused this?

Do I just need to replace the valve cover gasket and spark plug gasket/seal?
Also, do I need a new coil pack as well for this cylinder?

Thanks in advance!

When standing in front of the car, it's the third spark plug, the 3 others are fine:

 

You likely need a plug seal. They should come in the valve cover gasket kit. No new coil is needed unless that plug has a timing miss.

 

If it had a timing miss, I'd have a Check Engine Light, right?
I plugged the scanner on and it didn't detect anything

Do you know if it's easy to do on an IS200T?
I'm used to Honda/Acura (Prelude/Civic/RSX) so if it's like that, then this should be a walk in the park

 

Yes, on the CEL.
I have not replaced a valve cover gasket on a Lexus. You would only need to replace the gasket with the leaking seal. The front bank in your case.

 

Just an update if this happens to anyone else, I drained some oil out (it was pass the full mark for ~1,500 km).

I drove ~500 km and so far, no more oil on the new spark plugs.