Remington's website has what you are looking for.
$50 - $80
The value will be determined by the condition of the pistol. Anywhere from $0 to $500. In Mint condition especially in the box they can be worth double that.
$150 or less, depending on condition.
Yes, that would be the Model 51 made in 380 and 32 auto.
Manufactured 1919
Condition?
Click on the link below for photo Model 51
Depends on original condition from a $100 parts gun to as much as a $1,200 new in the box.
50-300 or so
$75-$100, depending on condition. Low cost firearm of indifferent quality.
100-1000 depending on specifics