It is 4.5 litres when changing the oil filter as well (which i'd expect you to do lol)
To be fair, Magnatec 10W40 is fine, but I use Quantum Gold (Now called Platinum) from the dealers, £25 for 5 litres and it's fully synthetic, along with a genuine filter for a few quid more.
It's very easy to change the oil, but mark my words you will NEVER be able to do it without spilling any oil anywhere! Maybe if you had ramps you'd get away with it, but jacked up forget it, it's mess central! But good fun!
When you take the oil filter off, you will need to disconnect the air pump electrical connector from underneath(you'll see it as it is blocking the way for the filter to come out!)
Do the oil filter up hand tight and use a bit of oil to grease the lip of the new filter.
When refilling pour in approximately ~4L of the oil then start the engine, let it run for a few mins, then turn off, leave for 5-10 mins, check the level, and fill accordingly. (DO NOT REV engine or anything like that when your doing this).
Then take some pride in your work and savour the fact you've done a decent oil change, and not a garage who doesn't drain the oil properly, and puts cheap oil in - not saying that happens much but it's peace of mind if you do it yourself
As said already, if your buying the car off someone who has kept receipts of everything they do, I value that just as much as FSH!