How to activate a Sprint Moto Razr bought from Ebay

I'm a tech noob and I don't know much about cell phones. Anyhow, I recently dropped my Katana in water and damaged it beyond repair so I got a replacement off ebay. I checked the ESN/HEX # to make sure it's clean before I paid. Anyhow, once I receive the phone, should I take the phone to the Sprint Store to activate it or should I do it online? Do I have to deactivate my Katana first before I activate my new phone? Do I just swap ESN/HEX #? Hopefully there's a techie here or someone w/prior experience that can help me. Thanks guys

Just call Sprint's customer tech support, you can do this over the phone, no need to go to the store.