About all I can suggest is to browse through the
SubSim SH4 Ships Downloads section, browse through the pages and see how many subs you find. I don't think you're going to find too many with much campaign though. That is a LOT of work to accomplish, and it is not easy coming up with ideas for a mission, especially in light of it being the "Silent Service" and there is not much info on missions from then, much less something that holds a player's interest and doesn't bore them to tears while they try to fingerprint the sound signature of whatever it is they're following...
[three hours later] "huh, 'magine that - it's a baleen whale."
As for translations, the internet is a good tool (ie: Translate.Google.com) in that regard. All of the Data / Campaigns / Campaign(GE) / PatrolObjectives / *.tsr files, and the Data / Menu / menu.txt would be the ones to hit. It will take a while.
