Seems like more of a Steam question than a Wurm question. But on the upper right corner of the Steam window you should see a button with your user name and the amount of in your wallet. When you hover over it it should say Manage Account, so click it and select "Account details". The account details page has your account name (which is not the same as your user name), your Steam ID, contact info, and other goodies. Make sure you have either a valid e-mail or a cell phone because when you log in on a new machine Steam will use those to verify your ID. You're going to need your password as well, so hopefully you have that written down. (I assume they have an "I forgot my password option" but I'm guessing if that's the case you need to reset the password and write it down before doing anything else.) As far as I remember, installing Steam on a new machine is not a big deal, as in Google "Steam" and press the big green "install" button that appears. I changed computers not that long ago and I don't remember updating Steam as being that big a hassle. But maybe someone has done it more recently and remembers more details. As far as I know all the game info is stored with your account, so you don't need to reenter any keys for individual games. But I've never dealt with third party keys or special setups like that so I could be wrong.

Sorry, I'll be more careful in the future. Thank you for the info.