Agreed the lines and such buried inside the machine can be a source of contamination. Cleaning those is a bitch. replacing them might be easier.
Mike did you ever set up replenishment? that's one of the best things about the CP-31 I think. Turn it on, fill the tanks, and let the auto-replenishment keep everything fresh. It's really as good as tabletop processing gets, I think.
Once I get it up and running I can make usually 12 to 15 different 8x10 prints per hour, which is pretty good throughput I think, considering the time to take to swap negs, focus, expose, etc.
I have a filthy CP-51 I need to clean up and get running someday soon. It was relatively cheap, but needs a full freshening, including some new rollers I think.