Egads!
I can't imagine playing anything in a church setting without sheet music.
I'm with Alex; record the song or obtain a copy of it and transcribe it yourself.
As for the trumpet you'll get many opinions but here's what it boils down to.
Understand that no matter what horn you purchase it's only a horn and will not play any better then any other horn until you have reached a certain level of proficiency on your trumpet.
You may want to ask yourself how serious is my playing going to be? If you only play in church and will not play anywhere else is your current trumpet getting it done? What motivates you to want a different trumpet?
I play the instruments that I play for several reasons. I can utilize them in many different playing situations and it was not a financial burden on me to purchase them.
Only you can decide what’s right for you!
Good luck,
John