Jim, I'm glad to hear you're familiar with the the "today we are going to speak Japanese!" stunt. Meldas 50 has a real personality, cryptic error messages and such. Luckily sounds like you have a really good Mori rep there, actually able to solve problems on an older machine.
DNC is standard
afaik, just a matter of getting the RS232 to communicate properly. Mine has Auto, Tape and Direct for running programs so no problem there. There are also two serial ports, one for parameters (marked "panel") and the other one for programs ("NC"). Do you have a memory card with the machine? Good for backups..