Couple Questions regarding 2009 335xi

Hey folks, new to the forum, picking up a CPO 2009 335xi in the next couple of days, upgraded from a 1.8t VW passat, so i should be having plenty of fun, just wanted to pick your brains a little, apologies if you feel most of my questions could have been easily answered using search.
Here goes

Anybody know about the warranty policy and modding, reading up on the JB4 and that will be picked up in the near future, dont want to lose out on a couple of free oil changes or other things in the name of extra horsepower, especially when the 300 will keep me satisfied compared to the 220 i had before.

Also doing some reading and im not quite sure if the 2009 xis had stock oil coolers put in them, im not planning on tracking the car, but it gets decently hot around here, would rather not have problems after a long spirited drive in the summer

Lastly the car is a steptronic auto, i wanted the 6speed but beggars cant be choosers, this car is just to nicely equipped to be passed up, also with the economy hitting the wall in 2008 not alot of leases coming back, so ill make do, what is the tranny able to comfortably deal with? 400whp is ultimately the figure i want, just want to make sure it can handle it.

Thanks for looking, thanks for answering, and i look forward to being part of the forum