100-1000 USD or so
5000$
You will need to contact Walther to find out.
1961
Yes.
Try posting at p38forum.com
http://www.p38forum.com/
Dieter Marschall's book on Walther has sn data in it.
250 or so
Try asking on the p38forum.com
Try the P38forum
about as much as your mother is to me!
Military P38s are dated from a 3 letter code, and not a serial number.