Can you read music? In my experience, you will save much time by simply getting a collection of carols and selecting the interesting ones. Start with your public library, then try a music store. Don't overlook hymnals.

If you can't read music, try this:

http://www.ylw.mmtr.or.jp/~johnkoji/hymn/xmas/

This site has both MIDI's to listen to and lyrics to read.