When he drops off your new phone and you switch it on, it will ask if you want to transfer data from an old phone. Just follow the instructions on screen (you just have to put them side by side) and your data will be transferred.
The number is related to your SIM card. I can't remember what size the 11 took but if it's the same as the 17, just put it in the 17 and that will be your number and your data on the new phone. Just obtain a new SIM with new number for the old phone.