The repair depends on where in the tube it is torn. You have to peel the zipper back to where the tear is, so you might have to take it apart more than you think. I use a speedy stitcher and modified the stitch so that I get a baseball stitch along the tear. Then I do a glue job from the inside. This works very well and am in the middle of a 14 inch fix right now. The best option is to do the stitching and repair at your convenience and then send or take it to a pro who can radio frequency weld a patch on the outside.
The basic patch will hold for many years, but if you are like me and use your gear to the fullest, a welded patch is the way to go.
Yeah, an extra aire cell is a good thing to keep on hand. I have never had a pressure valve, but am vigilant about letting air out of the boat when it gets hot during the day.
Claimer: Someone that makes a claim that they have been there and done that, can do anything you can do better than you. I hate "claimers"