As long as that phone is CDMA, not on the lost/stolen list than yah. It won't cost you anything or extend your contract. Just just vzw a call and they can swap it over.. Contacts/txt/pictures are all stored on the phone so you need to back them up someway first
You can also activate the phone online via your My Verizon account at your convenience.
Sign in to My Verizon.
Locate the I Want To... section.
In the DEVICE column, click Activate a Device.
Select MDN (if applicable).
Enter Zip Code (location) and click Submit (if applicable).
Enter the new Device ID (ESN, MEID, or IMEI).
Select the check box for the desired feature(s).
Review and confirm the selected updates.
You can also activate the phone by turning off the Alias 2 and dialing *228 and send on the phone you want to activate. When you hear the recording press option 1 to program and wait until you hear the message that the phone has been programmed successfully.