How to change aftermarket air filter on an 2008 Scion XB?

No one will touch my air filter when i get the car serviced. The places say that i have an aftermarket they won't mess with it. I bought the car in 2009 used and found out someone had put racing equipment under the hood TRD? I'm a 32 year old woman and have no clue about this. I thought the car was little peppy for a 4 cylinder!..lol Anyways if you can tell me how to get to it that would be great. Looks like i would have to disconnect the battery to get down to it or go underneath?