Do you still have the door tag warranty plate?
It will give more information about your car than the Vin number alone.
Here is all the information I could get:
Year: 0 1970
Plant: F Dearborn, MI
Body Series: 05 SportsRoof, Mach 1
Engine: H 351 2v V8
Unit: 125318 125318
Nothing new for you I am sure. About the history I don't think there is a way for you to find any information as comapnies like Carfax only have records for cars produced after 1980.
About the value of you car, it's not possible for us to do this without seeing your Mustang but a good way to check the market is to go on Ebay.com and see how much they are sold. They always have hundreds of classic Mustangs listed there.