restoring to take back for repairs

[watersa8]

hey ive recently suffered from the decreased sensitivity problem with the touchscreen on my iphone and am planning on taking it back to get fixed as its still under warrenty but with me having jailbroken the phone i just want to make sure what u need to do so that they cant tell its been jailbroken im currently running 1.1.3 and as i understand it if i just upgrade the firmware they wont be able to tell the difference do i need to do anything else?

[Safari]

Jusr do a full restore through iTunes.