Doug I used to make frozen yogurt all the time. I used lowfat or nonfat all the time and I also used unflavored and added my own.
There is a book I used (it's about 16 years old - don't know if it's available still) called "Mable & Gar Hoffman's Frozen Yogurt" which is great! (just checked Amazon and they don't carry it new or used.)
One thing to remember working with yogurt in 'ice cream' is to heat other ingredients, but not the yogurt itself - it can curdle - just add the ingred. to the yogurt.
IF you do heat it, be sure to use very low heat and stir gently - rapid stirring also encourages curdling.
As an example of technique I'm offering a Creamy Chocolate Frozen Yogurt - for you and Gina!!
2 tsp. cornstarch
1/2 c sugar
12 oz. can evaporated skimmed or evaporated lowfat milk
1 egg, slightly beaten
2/3 c chocolate syrup
1/2 tsp. vanilla
1 c. plain lowfat yogur, stirred
In a med. saucepan, combine cornsarch and sugar. Stir in milk and egg.
Cook & stir over low heat 6-8 min or till mixture coats a metal spoon.
Remove from heat; add chocolate syrup and cool.
Stir in vanilla and yogurt.
Freeze in ice-cream maker according to mfg. directions or the refrig. freezer method.
Makes about 1 qt.
hope this helps a little.
Oh shoot Gina - just noticed you wanted the other chocolate...white chocolate with macadamia nuts - I'll post one separately for you!!

(in the healthy forum!)