I don't think it's replaceable, but I'm not sure. However, I'm on a lease too and I'm honestly not worried about it. I doubt they'll notice, and if they do, I'll just say it was really dirty and I thought it was replaceable.
I will be performing this tomorrow and I'll be dropping in a K&N high flow filter along with it. Excited to see what kind of difference is made in sound and throttle response....I have the 6 speed manual.
Does it affect air filtration negatively once it's gone? Or is the main filter enough?
I personally wouldn't worry about anything negative from getting rid of the second filter. The regular air filter alone is plenty. I wouldn't be surprised if they added they second filter for restriction alone.