I signed up a while back to get this update early. It requires a 2 part online training. I had difficulty with the 2nd part slide 14 of 36 stopped about halfway through on my Mac Book Pro. I had to finish on my iPad - go figure.
After the training there is a quiz. Then you get your code for the updater. I had the updater already on my laptop, but you have to download a different one.
It requires removing the cartridge and unless there is at least 70u in the old one, a new cartridge. I had a bit of trouble getting my pump to the screen that allows entering the update code. Once that happened it was easy peasy.
When done, you need to restart the Dexcom on the pump, so have your code handy.
There is no need to change mobile. The App evidently recognizes the updated pump. I did a 0.1u correction bolus to try it out.
I only cussed a little, mostly at my cat who wanted to stomp on my keyboard during the process.
I realized another benefit of the bolus from your phone update. When I have my sunglasses on, the Tandem screen is blank. I suppose because they are polarized lenses. This is not a problem on my iPhone screen.