donutagain,
Failed to find these elusive well priced RB67 screens. Ffordes have a few in for £29 if you are interested, although some of them aren't ideal (they are specific screens for specific photography purposes, quite evidently):
http://www.ffordes.com/search/mamiya screen
However, since focussing screens are so delicate anyway and the thought of going near one with a sharp blade makes me shudder, I decided to not go down that route. Instead I bought a focussing screen from Rick Oleson:
http://rick_oleson.tripod.com/index-175.html
I'm guessing yours might count as a "Rolleiflex fixed hood (E and earlier ONLY)", although it would be wise to contact Rick first, who is helpful via email.
I bought the rule of thirds pattern, 6608. It's a decent screen for the money, it was brighter than the stock screen it replaced and good value considering the cost of the Beattie Interscreens and the Maxwell ones. However, although I reckon my close focussing is now better (because of the split image, which is very handy), my focussing skill when looking at the WLF from head height has reduced - I think the images don't quite pop as much on the glass, although that said I use it in less than ample light on the street sometimes.
Still, especially considering your Automat's screen is getting on for decades and decades, replacement or cleaning is probably essential. No idea about the mirror, the one in my 3.5F was clean and in great condition. I have read about TLR mirror cleaning (and how to do it properly) in the past on the internet, so there are definitely articles around. For cleaning my Yashica Mat's mirror, I managed to remove it and use a rocket blower to get rid of the bigger pieces of crud and gave the surface a quick wipe, which removed 50+ years of grim that had managed to get in. However, as I sent my Rollei for a service, Brian Mickleboro would've cleaned the mirror anyway.
