When I started to play in a P&W situation a few years ago, I couldn't improvise lead, or, more to the point, was very uncomfortable. But, the director wanted it (and I wanted to as well). In any event, still not great, but get by, because she was insistent. So take this as a learning experience.
A couple of hints. If you hit a note that is sour, slide up or down to resolve it back to the scale. Then, do it again later. Remember this phrase, "I meant to do that."
After a while you will learn that some of the cooler riffs you have heard are folks sliding or bending to resolve notes onto the scale.
The other thing you can say if you land on a sour note and stay there too long, do it again and just say "Oh, I was inserting a jazz scale."
I know that sounds stupid, but thinking that does take some of the stress off. And really, most people don't notice. After a while, you get better at it.
If you really can't handle it, just tell the P&W leader. You may have to quit, but if you think you are becoming a distraction to the worship, that might be the better route. But I thinking, you will be able to step up and handle what the leader wants.