When I registered with Namecheap/e-rice today, here's how I did it.
Went to namecheap.com, ordered domain, got it confirmed and in my account
Went to e-rice, ordered hosting.
Got the welcome email from e-rice
Took the DNS server addresses from E-rice's welcome email, went to namecheap's control panel, updated dns server in their records.
Currently waiting for DNS to refresh so I can start uploading stuff to the hosting account.
I imagine you'd go through a similar process with ripplehost. I went with e-rice because the control panel isn't all that important to me, plus you get 150mb storage/3gb traffic as opposed to 100/1gb at ripple.