You would have to have someone that owns eCart6 update it for you.
I could go in and do it in a premier support ticket, but you might want to consider updating to Dreamweaver CS6 so you can use our extensions moving forward to update your sites on your own instead of hiring someone else to do it.
It probably isn't just your cart that needs to be updated. It would be all of your database references on the entire site. If you don't plan on updating Dreamweaver, then I wouldn't update php version either.