Welcome to the asylum!
1) Look for a brand name or part number on the filters. The easiest solution would be to buy one identical to the roached one. Otherwise, I'd recommend a brand new pair from APE or K&N. This assumes that proper jeting has been done. You can look on the seller's web site for the correct filter for your bike.
2) Yes, no, well maybe. Rebuilding the forks is really not that complicated. Generally, the only difficult bit is removing the hex-head screw at the bottom that holds the innards into the outards. A pneumatic wrench is the best choice, but there are others.
3) The front brake should not be SHOCKING, but it will never equal the R1. My guess is that a rebuild and careful cleaning are in order.
However, before you dive into all that bidness (Texas pronunciation), I highly recommend acquiring a genuine Kawasaki Factory Service Manual, aka fsm. Also, a good set of JIS screwdrivers, or suitably modified Phillips screwdrivers. All those cross-head screws you see are not Phillips and can be really buggered by the wrong tool.
Others here will be along to harangue you about proper JASO_MA engine oil, fuel filters and Japanese Pixie dust..................................