Well there are obviously 3 main parts to consider:
- Have somewhat for the user to make a choice via the Uno;
- Play the sound based on the choice;
- Make the unit look presentable for the presentation.
The first step is simple programming. The simplest approach is to use a row or matrix of buttons. When the button is pressed, you do the action. Until you add the second step, just use the serial monitor and write a message or blink a LED. At a more advanced level, you could use a force or touch sensor, and do away with the physical button, perhaps even having a picture of the work over the button to guide the user. However, from your question, it sounds like that you've never programmed, and you probably want to stick with the basics.
On the second step, if you are only playing a sound recording and doing nothing else, you don't need the PC. There are shields such as Sparkfun's mp3 shield and Adafruit's wav shield, that you put the audio on a SD (or micro SD, I don't recall which they use) card, and hook up a speaker. Otherwise, you need to write a program on the pc, that opens the serial monitor and looks for commands sent out by the Arduino of what to play (the Arduino would just use Serial.print/Serial.println).
Once you have it all together, then you need to make it look pretty. This will depend on what your final setup looks like.