Do I have to redo the images and put in the right year or will the first 15 days that say "2011" be okay since it's still me who took them but I just forgot to change the year? I have already changed the pictures in my album on my computer. I just don't want to lose the comments that I've gotten for the first 15 photos of 2012.
watermarking images doesn't add any extra protection as to leaving them bare, if you took the photo, you own it and are the copyright holder for it, adding a watermark makes no difference. The only thing a watermark says is that it gives the impression you might enforce your ownership if somebody steals it, you can still enforce your ownership without the watermark, it's just how it is perceived i guess.
You should just be able to edit the photos and change the date without any ill effects. I moved the album some of mine are in and the comments stayed. But it you want to test with just one to make sure, then copy the comments to a word document first and you can always add them into your image description.