Darla, if you can afford a professional translator, that would be your best bet. It really is an art and the challenge with working with someone who doesn't do this is that it can go much more slowly and either not accurate enough or too accurate.
With Crucible of War, we had a lot of material, so split the translations of the transcripts between the director (who did speak the language while the editor didn't), two student friends, and two professional linguists. The quality of the translations was best with the two professionals, followed by the students followed by the director. He was simply too close to the material and his translations took a painstakingly slow amount of time and were too literal in text. Once we got to the point of editing, we brought in one of the professional linguists to work with us on the subtitles, both to help the editor get the cuts exactly right, improve the linguistic construction, and dare to lose some of the exact words to fit the space and still retain the meaning.