My suggestion to you would first be to PRAY. Then since your music minister approached you, go ahead and sit down with him to tell him your concerns. If you are leading the worship team, once you have the go ahead from your leadership, as hard as this is to do in a church setting, there really do need to be some ground rules. Especially when it comes to prayer and preparation for worship. Although God's anointing can do wonderful things, your team also needs to practice together!! Our worship team practices together on Thursday evenings for about 2 hrs. Then a short warmup on Sunday morning and sunday evening before services. This give us time to practice and pick apart songs we are learning and freshen up the ones we do often.
When I was directing the choir in a former church, I once had a potential choir member tell me that she knew most all of the songs we might be singing and that she didn't need to be at practices regularly and besides "when God's anointing falls on us, he'll take care of all that and we'll sound good anyway."
My response was that Sure, God can do that, BUT just think how wonderful it will be if we work hard and sound as good as possible anyway, how much more can God bless people through our music. It's all about being good stewards of the talents God as given us. As we practice, and grow and get better at what we do, the anointing will increase and God will move in a greater way through our ministering in music.
The study you mentioned sounds like it would be a great help for all involved and an opportunity for making the praise team aware of what is expected of them as a team.
In Christ,
Trish