You can set up a domain at dreamhost called ykfp.org just like you already have – dreamhost won’t ‘serve’ the site or confuse the internet until and unless you tell your domain registrar to point to DHs nameservers for that domain-- you won’t do that until your migrated domain is up, running (as a DH subdomain) and you feel ready.
By adding your domain at DH you’ll end up with a directory called, conveniently, ykfp.org – in that directory you’d recreate your existing site, probably using a tarball like you had in mind. But since the internet doesn’t know about your directory on DH called ykfp.org. that’s where the neat subdomain trick comes in. Add a dreamhost subdomain called essentially anything not already in use, maybe ykfp.dreamhost.com and have it point at your ykfp.org directory. Then when loading ykfp.dreamhost.com you’ll be looking at ykfp.org files. The more your site relies on relative paths to files and scripts, the easier it will all be. I had some hard-coded script paths and converted as many as I could to relative; the rest I edited to reflect the dreamhost subdomain while I tested them in the DH environment; then I edited them to the ‘final’ domain name after testing. Went to my registrar, pointed my domain at dreamhost nameservers, and (a day or so later) my site just started being served from DH instead of the previous host.
I’m fairly novice at all this but did go through the same thing recently so hope I got the gist of it right. There are many more experienced here and some other/better ideas may come up. Have fun. I like DH a lot.