Greetings from Finland again! My 2005 Gmc Yukon XL is working fine and in couple of months it will be summer

I am going to to a 190 000 mile service, what i should conclude in it? Spark plugs, belt, etc etc?

And about the tyres.. i have size 265/75/16 cooper tyres now. Can i put on 285/75/16 without lifting the truck? Its 2500 hd model.
What is the biggest tyre size i can have without any lift kits?