1) changing the image that is displayed when a different option is displayed will take some custom coding using javascript, you will need to hand code a javascript function that will trigger when the option is selected to change the image to the correct one corresponding to the selected option.
if you need help with this, I would suggest signing up for a premiere ticket appointment where we could work with you in a one on one session to implement this.
2) if you look at the eCommerce database that we offer, product options are implemented using a linking table to create a many to many relationship of option to product.
the productoptions table holds information that is unique to the option for a specific product, this would include inventory.
the inventory should be stored in the productoptions linking table.
