I highly recommend Pennzoil Ultra Platinum 5W30. But any reputable synthetic 5W30 is ok. If you really want to go for the most expensive, then try the Nissan Ester 5W30 which is designed to stop VVEL noise.

Upgraded gallery gaskets are never a bad thing. And yeah there is enough stuff you come across to get to the gaskets that you might as well put a bunch of new stuff in. My timing chain looked fine at 100K miles. We decided not to bother since I couldn't find one in the parts bin.

How long does it usually take to change the gallery gasket?

What's the part number of the upgraded gasket set?

You'll have to speak with your mechanic. I had a bunch of other work done at the same time and I did a bunch of the misc remove/reinstall of various parts and trim pieces myself to save some money. He just charged me by the hour so I don't have a breakdown of what he charged for individual elements.

Get the EPS gasket kit. It's got better gaskets than the updated Nissan ones plus their hardware is upgraded.