The C3k comes with one of the best Japanese <-> English dictionaries available.
If you have lost it in the conversion process then you should seriously consider going back to the Japanese version and converting the menus yourself.
Other good options are zten with edict, enamdict, life sci dic or Eijiro (you'll have to pay for this but it's pretty good - although most of the entries are in the C3k multimedia dictionary).
zbedic is also a useful dictionary app, but I haven't found many decent Japanese-English dictionaries for it (most of the zbedic dictionaries are in romanji )
I you want the Japanese input then you are probably best off with the Japanese version, although you may be able to relink the input methods in the englsih conversion
Stu