6.1.2 - 6.1.3 - 6.1.4

I'm running 6.1.2, with some minor mods here and there.

1. I want to upgrade to 6.1.3 and then 6.1.4. Will upgrading to 6.1.3 mess up my modifications or customizations, and, the site itself, will it reset it?
   
2. Is there a good set of instructions on how to upgrade from 6.1.2 to 6.1.3. And, from 6.1.3 - 6.1.4. Also, is it possible to go from 6.1.2 to 6.1.4 without doing 6.1.3?
   
3. Is there a changelog or whatever with a list/explanation the changes  in each version? So I know if its worth upgrading or not.

Do them in order! Mostly they are recompiling of the lang file. I don't see how it could effect your current modified site. However a good rule of thumb is to open up the Patches and verify that a file being overwritten is not a modified file. Since there is only 1 css file for classifieds in 6.1.3 I don't see a problem. And no css scripts in 6.1.4.

The changes are posted in the patch areas...They have introduced html pages of what changes from which script. Its a downloadable file and covers every change.