Check Earl's Repair Service. Probably about the most knowledgable Walther person in the USA. His web site has pictures ( not very good ones, though ) and parts diagrams of many of the Walter rifles.
Also check the International Walther site. There is a guy on there named Dieter Marschall (sp???) who knows EVERYTHING about Walthers. He wrote the definitive book.
These are really neat rifles, but parts are, of course, nearly impossible to obtain. The Walther plants and all the drawings and such were destroyed in the war.
Establishing a value is apparently very difficult, since there are so many CRAZY collectors that drive proces up. Dieter will not even speculate on value, seeing as how he lives in Germany. A lot of it is how much do you want it taking into account the condition, parts availability, etc.
I have seen some sell for $350 or so recently, but I bought one on here from another RFC supporter for less than $200. It had a broken piece ( the " ball " on the end of the bolt handle ), but I looked at it as a parts source for my other Model II.
I have seen others like the meister series of the modelV which is a single-shot for around $600.