You can remove your kit or you just overwrite it, doesn´t matter how u do it.
Copy the kit on USB stick in a folder called PS3, Open with triangle the USB stick on the PS3 and copy the files to your Harddisk. Start PES 11, select in Edit-Mode the Kits/jerseys and load the new brazil kit. Then copy it or overwrite it over your old kit. Hope this is helpful...