Can I change the URL of my inventory page (EG: www.aac.ourtires.net)
No. However you can install a link on your current website where customers can click on the link and be directed to the inventory page, giving you the ability to promote your own website with a live inventory accessible on it.
If you don't have a website and prefer to use a different URL for your webage, you can get a domain (eg www.yourtireshopname.com) for about $10 per year, and have the provider "Forward" the viewer directly to your inventory page. That way you can advertise (eg www.yourtireshopname.com) but the visitors will immediately directed to your inventory page. You do not need to develop a website to do this.