A newer model would have the gliding mirror, which reduces vignetting with longer lenses. I have a 501CM, so I don't know how much of an issue it is with the older models. I've heard it's not worth the extra money for most uses.
I would spend the extra money to get a model with the Acute-Matte screen.
The older chrome lenses are harder to repair since some parts are not still available. I would stick with the CF lenses, but I did buy a 250mm C, since the price was so low and I don't use it a lot. I like its quality and hope it lasts a long time. But if it fails and isn't repairable I only spent a bit more than the cost of a CLA on it to start with. That's something to consider.
I would recommend http://www.david-odess.com for repairs, unless you find a local repair man with factory training and some experience.