Not trying to tell you not to cook babybacks, but from my experience, spare ribs are more forgiving than BB's because they are not as lean as BB's. Only smoke them (spares) for about 3 hours spraying with apple juice every hour. Then wrap them in foil with some more apple juice and cook (in the oven, if you want) for another 2 hours. Then, remove from the foil and cook over an open flame to crisp them up a bit. If you like sauce, now is the time you can brush that stuff on. Make sure you flip the ribs regularly to keep the sugars in the rub and sauce from burning.
This is what people are talking about when they mention the 3-2-1 method. As you get more comfortable with all of the variables, you can change the times on the 3 the 2 and the 1. Adding to the 3 will add more smoke, but can start to dry out quick. More of the 2 will allow more meat to pull from the bone. But be careful because the meat can get mushy really quick (mushy is bad) by cooking too long in the foil.
Enjoy.