Why would the OP need to activate it? That requires a SIM. I'd personally "Erase all Content and Settings" and call my carrier to insure it's not tied to my account anymore then call it a day.
no you shouldn't have to open it however your gonna wanna make sure you activate back the current sim on the current line back... by either calling in or by having some one in store do it... no need to activate the new sim just sell it sealed you will probably get more for it this way...