haha...I see you are downloading it now..there..more bandwidth.
First, not to worry, whatever you do can be undone. I've borked my phone more times than days I've had it so far because I was experimenting and learning. After the nth wipe/rebuild, it's just peachy.
- I've seen that method on Droid Life but it seemed like it could cause problems or not work at all (feedback) so I avoided it. There is a thread on xda with some mods that will properly get rid of it; it has a few zips attached. I'm using the ICSBlueFull.zip one but there's another one that removes WiFi notification.
- The only potential issue with root is to be sure you update the Superuser app (from the play store, it should automatically pop-up on first boot) and actually launch the Superuser app once; otherwise, it may not actually grant root access. (This was my observation.)
- Don't take OTA updates if you've "modified" your phone in any way, to include root access. I'm not saying it won't work; others have said it either won't or you'll just lose root afterwards. I'm saying, "Don't tempt fate." and do a full wipe, reinstall and configure everything manually. It's cumbersome at first but it'll avert problems later and keep you from wondering if something does go wrong. (I admonished against Windows upgrade-in-place for the same reason; just reformat/install instead.)
- re: long post. That's never a problem. Tip: add some white space.
It looks like your download is finished. Before you Odin flash it, format internal storage, factory data reset, wipe caches. You can format external storage, just make sure you copy anything you want to keep from it to your PC first. You can format /system but you'll have to pull the battery to reboot.