Can Mercurial repositories safely be moved/renamed/etc.

pgs is entirely correct. When you create a project at Google (or other hosting services), they will create a repository for you. You need to copy over your code, add it / commit (after tweaking .hgignore, of course!) and hg commit -Am "Inintial checkin of project"

If you try to push another repository that you create to Google, it will not work. This is because your newly created repository is not related to (derived from) the one that Google created for you. Since you don't have CLI access to Google, you can't do the usual work-around for unrelated pulls by cherry picking particular revisions.

This is frustrating when you already have a repository with history. In that case, you have to clone the empty Google repo, then hg pull (path / url to your repo) to get your revisions, then commit, then push. Good luck with that if you have extensive branches, be sure you have no unresolved heads before you push to Google.

This is why I host my own hg repos on my own site, much less hassle.

It's equally easy to install HG on Win2k3 and 2k8 (with the exception that you'll probably have to take the extra step on 2k8 to "run as administrator")

My favorite tutorial for Mercurial is Joel Spolsky's excellent HGInit The "Ground Up Mercurial" and "Setting Up For a Team" sections will be of the most use to you.