Decompiling an APK is somewhat tiresome process, you have to first extract it, then run it through a smali to java convertor and after you edit the resource files, you have to again repack it. All these processes can be automated by using Virtous Ten Studios.
It is like an IDE that will help you to change the resouce files and see the source of the file easily. And since the UI of the Ten Studios looks like Visual Studios, you will be able to understand it pretty darn easily.
http://www.virtuous-ten-studio.com/. You can buy a pro license to support the developer.