It looks my Focus is suffering from the same problem with a blown resistor box due to bad bearings in the blower fan, as it was quite squeaky when the lower speeds still worked.

The question is now if I should try to fix it myself or pay to have it fixed. It should anyhow not be too difficult to find a used fan replacement.

I have seen the nice pictures of where to find the resistor box but now I wonder if there is there someone who can get me a hint how to replace the blower fan. How do I access it?