I'm making a custom Google Map, using the official Styled Maps Wizard.
However, it doesn't seem to be possible to change the font-family of the labels (which is Arial).
Does anyone know if this is possible in Google Maps?
The answer is: it can't be done. The best you can do is switch off all Google Maps labels, and use custom overlays.
Alternatively, make your own tiles using a service like Cloudmade or TileMill.