Fairly certain you'll need to remove the entire dash to get the cluster out. You can apparently get it out by just loosening a few bits but it looks very tight. Have a look on YouTube for C5 cluster removal, there's a few videos on there of how to get it out.
I looked a long time ago when I wanted to change the bulbs, been putting it off ever since it looks like such a PITA! Oh and if you do pull the cluster out don't leave it face down.