Pete Nice

I've just broken one of my two key fobs for my Qashqiai 2011 J10 and I want to get a replacement and program it myself. I've seen a method listed here and on a few other sites. I have a few questions around this: 1. When reprogramming do you have to do the new fob and existing fob as I've read it deletes all saved keys so both need to be programmed together? 2. Is there any issue around the immobiliser with the self programming method? TIA