Hi Stacey - At the top of the listing creation page there is a drop down menu labeled "eBay site". You will find eBay Motors listed there. Select that site and the page will refresh with new catagories specific to that site.
There has been a significant increase in scams on eBay Motors recently. In case you want to brush up on the latest scam info regarding this particular marketplace before you list, this site addresses the situation at length:
http://www.ebaymotorssucks.com/index1.htmand of course I'm sure you've looked here:
http://forums.ebay.com/db1/forum.jspa?forumID=20