Does anyone know what is output to matrix orbital LCD' s with a serial input? Is it just pure ascii?
I would like to see if it is possible to hook up the empeg instead of the MO display, and have the info on the empeg's screen.
I imagine this is going to require a lot more programming than I currently can do, or think it will need

You can view the manual for the MO displays online. here is one.

I don't know about using an empeg display. I would assume it is parallel and not serial, but there's probably even more to it than that.

With the limited command set of something like the display Rob linked to, it wouldn't be too hard to write a program to 'emulate' it using the Empeg's display.

Basically you would open the serial port and wait for incoming data, figure out what needs to be done (based on the command set of the display you're emulating), and do that thing on the Empeg display. You'd probably want to use vfdlib and maybe make yourself a custom font that matches MO's.