Why should the app size be huge because the sound files are huge? You probably don't want to "embed" the sounds in the app, but have them as separate files that the app reads from the Android device and plays as necessary.
Start by learning how to create an app with a button that plays a specific sound file. When you have that working, start looking at random numbers and indexing the files via a random number.
And as for updates, a quick google will get you started:
android update apps java - Google Search[
^] - plenty to read there!
Submit an article or tip