When installing a new version should I uninstall the old one first,
or can I just install the new on top of the old one?

Also which version are we gonna use on the upcoming March 10th match?

Just install over the old version (I suppose that you use the standalone rather then the branch release?).
The version from the official match will be 0.83, which has just been released.

You can overwrite over the previous version most of the time. You can't when there is a really big update that changes a lot of files (like the introduction of overlays and packages).
It will likely be played on 0.83.

Thanks. 0.83 installed painlessly, just wanted to be sure.
Branch or standalone idk? I'm using the installer from Desura.

Ok then it makes it automatically anyway, so you should be on the safe side