Impossible to answer without a detailed description of all features, condition, finish, box, papers, accessories, etc..
Impossible to value with only the serial number and no other information.
100-500 USD or so
Requires hands on appraisal
1981-1985
Anywhere from $300 to $550.
The best reference is the Standard Catalog of Smith and Wesson, 3rd, ed. by Supica and Nahas
1970; 75-400
$100-$450.
50-450 usd
50-500 usd
100-500 or so
You might have better luck asking at smith-wessonforum.com