Gleaner L injection pump woes continue...

I've had a lot of trouble getting my Gleaner L running. Finally figured it was the injection pump and had it rebuilt for $875. Once it was installed it ran great for about 20 minutes then suddenly died. I thought bad fuel had clogged the filters. I started into cleaning the tank, but it was so full of tar I just bought a new tank and I replaced the filter. After all that I couldn't get fuel to the injectors. I took the injection pump back off and took it to a shop and they told me the shaft broke! Also that parts in the newly rebuilt pump were rusty. What happened to my pump and what should I do?

Does anyone know where I can find a Roosa Master pump (model number DM4629JT3080) for cheap? It is starting to look like my wheat will not be harvested by a Gleaner this year.