...and 12 hours later, I decided it was easier to rebuild it from scratch.
I just took the images for the header and navtabs, etc and built my own version as a child theme of my board's main theme, using the Pure Christmas templates as a guide. Couple of hours of fiddling with the CSS file and stylevars... and I have something I'm very happy with.
Not a faithful replication by any means, but it is easier to maintain.
Now... on to the snowfall!