changing domain name and purshcasing ssl cert

I am trying to change my cafecommerce store name. I have made the initial switch for most of the pages but when I try to buy a new SSL Certificate I keep getting an error saying that my domain is currently connected to another service on Dreamhost, however I had Dreamhost convert the hosting of the new domain over to CafeCommerce already. I have attached an image of the error i get when trying to purchase the ssl cert and an image of the dreamhost manage domain page.

Small sidenote. I did purchase an ssl cert for the domain through dreamhost as well, but have decided to abandon that route as this process it too cumbersome to go that route. I will be fine with purchasing the cert directly through CafeCommerce.
Thanks for any help on this issue.

Since your domain is already set up, you should be scrolling down on that page and clicking the "Purchase Certificate" button. It looks like you are clicking the "Purchase a Domain" button instead and that isn't necessary since your domain is already registered with Dreamhost.

Thanks Ray,
So I did that, but I am not getting the feeling that the new domain, the only domain I want to be used, is going to replace the old one. The reason why I say this as that in the admin panel I still have two url's that can access my store. One of them contains the old url. How does one remedy this? When people go to checkout of the store are they going to go the old url space? I have attached an image of why I am concerned. The olde url is highlighted.
Thansk,
Heidi

I updated the domain... it won't actually go there in checkout any more since you have your own SSL certificate, but I updated it anyway.

Thanks for doing that Ray. It looks like at this juncture I am safe to delete the old domain from being hosted on Dreamhost? I just want to double check because the last time I did that I lost access the store and everything, so i am a little gun shy. See attached image for clarification.
Thanks!
Heidi

Yes, you are safe to delete the old domain