I got the computer. I left to Rotterdam at 8AM, and just got back, and all in all (with the electric car from yesterday) spent around 60€ on transportation, but it's still worth it. The guy's house was super messy, and the computer is really gross, but it works (I asked him to show me) and I picked up some hardware cleaning supplies on the way.
I had to do some other things during the day at Sandberg, including setting myself up a proper workstation, but the computer is cleaned and ready to go. I also removed the case for now, I want to experiment a bit with it. This meant I also took off the on/off switch, which was embedded in the top case. Note to self to put that back correctly! I am now going to install Ubuntu on it for now, and want to try to set up the reverse proxy tunnel on it, so I can SSH into it from outside the school. But first things first.
Installing Linux from Linux is quite easy, at least in my case, using Ubuntu. Download whatever version you want, I went with Ubuntu, and use the App Startup Disk Creator, which comes with Ubuntu, to create a bootable USB drive. Ideally we just plug that into the new machine, boot it, and that's it.
The login credentials are (for now)
un: SalwaServer pw: SilverSurfer!