Rejetting will not be necessary, the difference in flow a replacement filter alone makes isn't enough to affect jetting in any measurable way.
If it's a new filter it should come pre-oiled. With a k&n it's simple to tell if it's oiled or not. It's a white cotton filter, and k&n oil is red, so if the filter looks red you're good to go, if it's white you need to oil it first.
I will warn you though, that the stock filter setup is a severely flawed design in my opinion, it's far too easy to install the filter incorrectly because the airbox lid is supposed to hold the filter tight against the seat and keep it sealed. First, make sure you put some grease on the foam seal to help it seal correctly, and when you put the lid on make sure you start with it too far back and slide it towards the front so you catch that top ear of the filter and push it tight against. Just dropping the lid straight down usually leaves a 1/2" gap at the top which kinda defeats the purpose of even having an air filter. When I had the stock style filter I always installed it with the snorkel removed from the airbox, so that I could see that the filter was sitting correctly after I put the lid on.
. Pushed the warrior home and ordered a pro-flo kit.
