Unsure of Updating N360 process

I'm using Windows7. Norton360 is already installed on both my desktop & laptop computers and is about to expire. I just purchased a Norton 360 CD from Staples, so I have a product key. I want to install/update on both of my computers.  Last year I had a lot of frustrating problems that I'd like to avoid this year.  I'm leaving on a trip day after tomorrow & would like to get this fixed before I leave.  I doubt I'll get both computers done.   Suppose I don't . . . does the currently installed version continue, but with limited protection?

  • Should I use the Norton Removal Tool (from Symantec.com/nrt) to remove the existing version?
  • If I remove the existing Norton, won't I be vulnerable while I'm online downloading the new version?
  • Is it possible to just submit my new product key to extend my subscription? My current version (on both computers) have the latest updates.
  • Do I "download" from the internet or load from the CD & then run updates? I was told last year (in the forum) that I should have only used the product key from the CD & download everything else.  Either way is a time consuming task.
  • If I "download" can I "save" (instead of "run") to my computer & later "copy" that offline to my laptop?