You will need to completely open the A500 to see the ROM. Here is a picture:
To the left of the big white A500 writing there is a vertical long chip - the smaller of the two (just above this chip is a silver thing - this is a crystal, but you don't need to worry about that). This long chip is the Kickstart ROM.
I couldn't find a guide on the net, but someone here will be able to help you.
