You will not find a complete schematic out on the internet, you may find a piece or two, but the schematic is considered IP so has never been released I'm sure.
I don't know a lot about conversion options, which is why I am here personally, but that would be my suggestion as well. I know that the PLM2000 utilizes an Animatics drive for those servo motors and if that is not operational, a retrofit is the only option.
Inexpensive is also relative - For some $1500 qualifies, for others $15k can be inexpensive!