310,000 km zero maintenance records 2010 RCSB 5.7

So what I'm asking is what would be the maintenance items I should tick off to get this
motor baselined? I'm new to the computer generation engines as for the last 15+ yrs
I've been maintaining 1988 JDM direct injected diesels.
But after being away for two months the second week after I bought it, the battery is dead.
I've got an OBD reader and have figured out how to read the codes and check efficiency.
But I've read keep the MAF clean, etc but need more info.
Right now the battery is on charge and it's not got enough crank to start so new battery will
be here in a couple of days.
If ya had a few hours what would you recommend I do or what would anyone do to clean it
up?