ok
so if you want to know how to make a launcher, you cant just find a tutorial, because most people make it from scratch.
yes, the launcher is just another app, with a transparent background (that way you can see the wallpaper), and it reacts to the home button.
but how does it work, well, if you are smart, you are using eclipse, right. well now, get hold of a launchers .apk, such as using android assistant to back up go launcher ex as an apk and then transfering it to your pc, and then importing it to eclipse. that way you can look at the code and attempt to use bits of the code for what you need, but as far as graphics are conserned, you would need to use photoshop and set the workspace to "your screen hight x width", and then working from their.