New x5 owner, oil leak (alternator bracket)

[TerryZ91]

Hello everyone,
I recently acquired a 2005 x5 4.4i. The car has major oil leak. From what I can tell, it's coming from the alternator bracket gasket/seal. I heard this is common. The few questions I have are:

1) how hard is it to fix the oil leak if I do it at home. I found some DIY already. But I heard some people saying that they had trouble doing the work at home and it was very hard. I know the front differential have to be removed. Is that hard to remove? I have tools at home and I'm somewhat familiar with cars in general. I have changed the timing belt and also done suspension work on my honda. I know this is completely different and it's my first BMW so I want to see if I'm better off avoiding the headache at home and letting the mechanic do it.

2) since I'm already down there, should I do other repairs/maintenance that may arise in the future? One of the BMW mechanic recommended changing some gaskets, valve cover gasket, oil pressure switch, timing cover. Is the anything you guys can think of that I should do? The car has 90k miles. I heard some people changing ccv valve?

3) I know the 4.4 engine came with timing chain. Does it require replacing it at 100k miles? What about the water pump?

Thanks in advance!
Terry