puttin in my worthless two cents!!
When I first started recording drums all I had was 3 sm57's,so I'd put two in a xy configuration above the drummers head and one on the kick.It yielded suprising results, a little thin but better than nothing.So use them if that's all you've got to work with. As far as how many mics are necessary I believe in the philosophy less is more.If you can record with 2 to 3 mics and get the sound your looking for then do it.I personally use two for overheads,1 for kick, 1 for hi hat, 1 for snare.If you can use less mics you will have less phase cancellation, and the less mics you have to mix down the easier it is to keep it natural sounding.The only issue with the 57's for overheads as far as I know they do not have the ability to accurately follow the high transient response given off by cymbals.This would probably be best answered by Harvey.