Got my first Lexus, Any tips?

I was able to purchase a 2012 Lexus IS 250 for a good price and from a reputable dealer. The car has 100,000 miles on it and only one owner to its name. It also had very good service records and maintenance. The exterior/interior is in very good condition. No problems with the engine that I can tell in my limited time with it. My question is does anyone have in tips on

  1. Maintenance (I really want to get the most out of it and have it for a while)?

  2. What I should do right away ?

3, Is it worth trying to upgrade it to have better performance (if yes, what should I start with?)

  1. Best way to wash it ?