Specialty manga stores or comic bookshops could be a good place to start. Sometimes they have rare or specific box sets like the one you're looking for. You can also check their websites if they have an online presence. Additionally, some conventions or comic expos might have vendors selling such items.
If not under warranty, you could try to fix it yourself if the damage is minor. Maybe some glue or tape could do the trick. But for major damages, it might be best to look for a professional repair service or consider buying a new one.
Sure! A lot of manga publishers translate and release manga in English to reach a wider audience. You can find them in bookstores, online platforms, and libraries.