well it really depends how thorough their check is but you should at the very least take the apps off your springboard and uninstall summerboard and dock before even walking in to an apple store
and i guess you should be able to but just use customize to fix the carier logo and anything else
You should virginize your phone if they find out you hacked your phone youll be black listed from apple. You can always unlock your phone and add the apps again but once youre black listed it can be for awhile or forever