If you go into .minecraft/bin there should be a java file called minecraft. This can be opened with WinRAR or 7Zip and there will be a bunch of files. One of the folders is called gui and contains the files for the UI. These can be edited there and then, or you can copy the folder over to a zipped folder in .minecraft/texture packs and then edited to allow you to toggle them on and off (to do that, click the Texture Packs button on the main menu, and click the one with the same name as the zipped folder you created earlier). The image files can be edited in the image editing software of your choice, as long as it supports transparency (not MS Paint, but most others work).
Oh, this should also probably be in the Texture Pack forum, this is for character skins only :smile.gif: .