Gonna service my car next week, what should i do ?

Hello

Bought an 2007 (56) albi blue 197 with 20k on from auction, it had the service light on when i got it.

I have now cleared the service light but want to do some work on it next week, i have read the oil change guide, how much oil do i need ? 5.3l or 4.7l ? there seems to be some disagreement in that thread?

Which oil should i get also ? doesn't seem to be a consensus on that ?

I also plan on changing the air filter ? should i get a standard one or an uprated one ?