I searched a little and did not find anything interesting. I'm looking for a guide on how to install Mercurial server with a nice WebUI.
CollabNet Subversion under Windows to the Edge and I'm happy, but a lot of people write and say that Mercurial is better, so I want to evaluate this myself.
I am looking for a tutorial, or for any WebUI for Mercurial.
I'm not entirely sure how feature-rich you want the Web UI to be, but a good place to start would be with hgweb.
The simplest way to get something up and running is with the built-in web server from the 'hg serve' command: https://www.mercurial-scm.org/wiki/hgserve
If you want something a little more involved for multiple repositories being served through a web server like httpd, here are some initial instructions to take a look at: https://www.mercurial-scm.org/wiki/HgWebDirStepByStep
If you need something more like a local Github, maybe take a look at RhodeCode (disclaimer, never used personally)