|...with fear and trepidation|
But, if your church group has a piano with a problem and really can't afford to shell out the bucks to have the keys unstuck because it's not one of those "key" pianos, there's no need to let the piano go to waste.
If you are careful, keep track of what you're doing and have average fix-it guy skills, it's really not that hard to do. The problem is 99% of the time simple swelling of the keys due to moisture. Pianos don't like outside walls, for instance and that can cause the problem.
First, check the piano for obvious broken keys. You probably want to hire a piano guy for that. If, however, you just have a swelling problem, here's how to fix it with simple tools. I've written a second article on the subject that also includes pictures. Let me know how it comes out for you.