Ok, I searched that thread at modmyi and found Post#38674 (yes, that's a rather big number!) and I quote (in the "Wallpaper.html" file):
"ok go into the html file, and use the search button, and type in "temp .... now hit the blue search button two more times and you are there. it will say value+ "c" change that to f."
So if your file has an "f", change it to a "c", save, re-spring, and hope for the best.
I think this is the location:
.innerHTML=tempValue+ "°f" + " " +
There's also this:
" <p id="temp">°C</p>"
Good luck!