I have never had a need for this program, but I will take a shot in the dark, based on what I know about how Linux works.
If you use the locate command ("locate sun-pinyin" I think would be the syntax), you should get back a list of all the sun-pinyin files. From this, you might be able to figure out the location of the dictionary so you can edit it. It's probably in /usr/share or /usr/lib (or the equivalents). Sadly, I am not competent to translate this to another language.
Again, this is just a shot in the dark. I have no idea whether it will work.
Good luck and welcome to Linux Questions.