I had a couple of these machines when I ran Compix Photo Agency in Miami. When I allegedly retire a few years ago, I kept one machine for my own use and it's still humming right along.
It's a very good machine but can be temperamental. They seldom really break down. When they stop it's usually because of dust on the slide sensor. They were designed to be used with Loersch plastic mounts (the worst on the planet) and when you use paper mounts - which I did for 20 years - dust gets swept down the sensor hole in the track (underneath the black plastic square near the chute) and blocks the signal.
This problem was not helped by the idiot who wrote the software for these machines - a German guy whose knowledge of English could be written on a pinhead. Once you figure out what he's trying to say it's OK but at first it's a bit like trying to crack a safe.
The ribbons are a simple calculator ribbon and can be found almost anywhere - even Office Depot. Star Manufacturing (which made the entire print head assembly) makes them and the part number is: SF01B for Star DP8340, DP 832-834. Unicorn Ribbon also makes them: #GR24.
They cost about $1.25. Or you can get the same thing in a different box from Loersch for $16. They all come from China these days.
Anyway, if your still looking for help and have not chucked the machine in the dumpster in desperation, let me know. I'll be happy to help.