I was following this tutorial trying to set up keys so I can log in without a password http://linux-sxs.org/networking/openssh.putty.html
Problem is, I followed his instructions except, I generated the key locally, and unless you did exactly as he said, you lock yourself out, which I did (had the "oh crap" moment after I d/c). Now I'm locked out. Is there any way I can backdoor into the server to undo what I did or do I have to start over?
You can use the Linode Control Panel. You should be able to access the server with Lish in order to edit the SSH server's configuration.