Limelites -
Unfortunately, the Cat Dressing stylesheet will do nothing for the expanded categories sidebox, because most of the tags are different, and there are elements in each mod that do not exist in the other one. I am thinking about how to combine Cat Dressing with the Simple Categories Tree mod, but don't expect it any time soon.
V2.0 may be easier to get this functionality from. (SCT can definitely do it, but I'm not sure how much of it will transfer to v2.0.)