Mr Click Click Derk
Here is a page to get you started, you'll need apktool: http://www.miui-au.com/add-ons/apktool/Where can I learn how to do this? I want to be able to change my navbar size by editing values/dimens.xml. I have no idea where to look to learn about compile
You'll want the latest aapt.exe from the Android SDK, so if you don't have that, you'll want to download/install that too (Android SDK that is). The aapt.exe file that is in the Android SDK will need to be copied and pasted into your apktool directory, replacing the aapt.exe file that comes with apktool. Then you should be able to decompile/compile apk's as needed.