Ok I got a few questions for the experts.. or knowledgeable noobs

Basically a diving into theming mission..
Ok, I'm wanting to theme some of the apps icons i use alot for #2 rom for starters.. (basically just greyscale/tweak em to match in the app drawer / homescreen better..) i'm guessing i can just yank the png from the apk and replace it with 7zip.. know i can push the new apk through cwm (to make it user friendly) but my questions/concerns are:
1 - will the new apk automagically just work being pushed to the data/app dir (think thats the right directory, long day)
2 - is there a way through cwm to modify an apk (just overwrite the existing icon) reason i ask that one is some apps are constantly being updated and i don't want to go through it every week (ie GoSMS, etc)
Thanks guys.. I appreciate the help..
and to mrast, don't let that thread discourage ya.. not trying to rehash anything or put my beliefs / thoughts / religion / personal views etc on that out there but you can NEVER make everyone happy 100% of the time.. if it looks good and people want it they will download it

take it as a grain of salt, not personal.. hell i think some of the themes are fugly but i'd never say that cause someone took their time to make it and they like it and are willing to share .. android and this community give us the option to make our phone our own.. anyways..