Most Chinese programmers are highly fluent in English. Remember, programming languages work in English, anyway.
It's pretty easy to start creating your own theme. I just added my own header and some little things to my site already. But if I wanted to download a new theme and install it, then I'll have to start from scratch again.
After adding the header, I found moving the search box down into the "Board Index" box helpful. Really, it took me a couple weeks to digest even a little of the inner workings of phpBB3, so I can't brag much. I'm thankful it's all open source, right? The comments inside give some good instruction on how to keep the original designer's intentions clear.
I'm still looking for that elusive original style. How can I make a forum that doesn't look so much like a forum, so people will be a little more interested in getting involved?