This is covered in your Owner's Manual, if you have one (stashed under the seat).
Otherwise, this site has the Service Manual - give it a download and a good read. The air cleaner info is on page 4-5.
I caution you NOT to buy a generic air filter, or any filter not provided by your Honda dealer. There's a LOT of supposed "Honda parts" out there for sale, and some air filters are too restrictive.
I personally recommend a K&N filter, if you need to replace the one you have.
In regards to your fuel - your leakage location (just below the fuel on/off switch) is odd, since the leaning of the bike shouldn't affect that part. I have a suspicion that the leak is elsewhere. Give your bike a good looking over, and let us know.
Regardless, I recommend that you get in the habit of closing that fuel valve anytime you shut off the bike.