Modifying android system apps Does anyone know a good articles or tutorials explaining how to go about it?

Do I need to recompile android sources after modifying system apps and then install them on my emulator device somehow?

Or maybe the process is much simplier than I imagine? (What I mean is just creating an apk and then just installing it on the phone?)

Thanks a lot in advance!
If you've got the AOSP source, then just import the app into Eclipse/Studio from packages/apps in the source tree.  Then you can modify it an run it on one of the emulators (a/k/a AVDs) or a real device connected via USB.

If you want to replace the system app in the build, then put your modified code back into packages/apps and rebuild the system image.  Otherwise you can just install and run it alongside the 'real' app.

FYI, if you get into this and have more involved programming questions, you should probably post in StackOverflow with an Android tag.