Okay, I'm replying to myself. I figured out setting up a repository, installing TortoiseSVN, and connecting. Believe it or not, with very few snags everything's working fine! I added basic instructions to the svn wiki page. http://wiki.dreamhost.com/index.php/Subversion
The only remaining issue is that authentication isn't being cached, so I get prompted repeatedly for my password. From what I can tell, saving passwords is enabled by default in Subversion config, and I tried setting it to yes in my personal config file (in ~/.subversion/config), but no luck.
Anyone? I've also reached the stage where I probably ought to contact support... I'm not even sure if they're supporting this yet. (Yes, I noted this on the wiki page).