Disclaimer: I do not host any domains outside of DreamHost so I am relying on the wiki to answer your questions.
1a) You are correct, register with another registrar, then set the nameservers to point to
This will allow you to keep the registration elsewhere, but use DreamHost to manage the DNS records, and host your site!
Modifying your domain's nameservers takes about 1-3 days to propagate across the entire Internet.
1b) Sign up for DreamHost hosting (assuming you don't already have an account); in the sign-up form you will need to select the option that says that you already own the registration and you only want Hosting
1c) Add your domain here https://panel.dreamhost.com/index.cgi?tree=domain.manage under Full hosting. And you are set!
2) I don't think so.
That page does not apply to your situation. There should be a wiki article for a setup like this. I think I'll make one. Is there a page that already exists for this that I missed?
Please let us know if this worked well. If you have any other questions, just ask