How do you make ganis with custom graphics?

[Prentice]

I'm trying to make a cool NPC that makes it so that the character is piloting a huge mech but I need to make custom ganis....how do I import custom graphics into the Graalshop?
also I wanna know if theres a way that the player would be able to detect incoming objects (mechs,missiles,whatever...)and If it detects something I want it to play a certain .wav file....
Please tell me the script to do that....I've been trying to find it out.....but I couldn't...