Jim and I are busy learning the Durufle. Jim found this website, "Single Parts" which has learning tapes that have the individual parts sung by a professional singer over a tape of an orchestra playing the Requiem, and a chorus singing it in the background. The website advertises: Personal study CDs for practicing can be used with or without your choral music score in hand. Learn your voice part's rhythm metrics and foreign language pronunciations from the teaching singer. It is a bit pricey, but Jim and I are finding it very useful in learning our parts. It has the advantage of having the notes and words in the context of the music so you can learn even without the score, such as listening in the car, or while on a walk.
I thought others might find it helpful too, I did run it past Mitchell and he approved. Here is the link: http://rehearsalarts.com/index.html