go for mac pro if your church got alot of money .

1) Would the MacPro and Final Cut Pro able to do the job?

Yerp. Enough said

2) If yes, what kind of other hardware I need to purchase? Video Capture card? If no what are my alternatives?

If you bought mac pro , there's no additional hardware/device needed

3) Do you think an iMac would able to handle the job?

Yerp, but not power as what mac pro has

4) What are the extra cost I would be looking at for the added hardware.
just use your digicam/videocam to record the scene . The rest , let Mac to do the job