Justin, I just did a DNN upgrade on a test site form 4.9.2 --> 5.0.1 and also upgraded the Catalook trial version 5.8.1 that was already installed from to the DNN 5 version. So far everything is working great. I didn't test them all, but skins that I tried worked, including the blue metal skin.
I understand this isn't much help in solving your problem, but the skins do work with 5.0.1.
Ed
Justin, when you say yellow text on white background, that sounds like the Demo Version notice that is displayed in the ItemPane and MenuPane. That will go away when the license key is applied.
You can take a look at the test site I referred to earlier here. It's something I just started working with this afternoon and is only for testing, so don't expect much. The Store tab opens a Child portal with the shopping cart. I will reset permissions to Registered Only in a day or two, but if you want to take a look, feel free.
I'm just learning Catalook too, so don't really know what's going on with your site. I haven't encountered any formatting problems like you have described.