Hardware/Software Solution Live-Editing with Multiple Feeds w MacBook Pro

*The Goal*
Record church service, during service, key/switch in Powerpoint slides and/or key in scripture references or lower-thirds. All of this would be 'live-edited' into one timeline where I could just trim any edges and burn to a DVD later and convert it to a web-ready format.
Eventually it'd be great to burn directly to a DVD while recording it to hard drive for web conversion. But that's not necessary now.

Question
Anyone have any suggestions for an inexpensive software/hardware solution that can:
A) have a camera and another feed (computer screen output [powerpoint, etc]) connected to the Macbook Pro, and a software program can record the feeds onto one 'timeline' by switching between the feeds?

B) camera and feeds connected to an external switcher and that connected to the Macbook, which has software that records the single feed, while the switcher switches between the feeds and/or keys in graphics, lower-thirds, etc.

Any suggestions on what to use?

I've heard of the Newtek Tricaster which sounds awesome and it does everything I'm looking for, except we can't afford $5,000+ right now.


My System
Macbook Pro, 4GB, 200GB HDD (7200rpm), 17"LED Hi-res
I purchased Final Cut Studio, which I realize may not help me in Live situations, but maybe there's a plugin software for FCP?

Thanks for your expertise. Please let me know if this should be posted in another forum section...

:: efrain