Ruger's web site has sn data.
400
50-350 USD or so
100-400 or so
i see them on auction for around $500 all the time
100-1000 USD or more depending on specifics
Call Ruger and they will tell you. SN info is also on their web site if you can access it.
75-1000 USD depending on EXACTLY what you have.
Ruger uses a model number, such as 0804, but the suggested retail price of a new Super Blackhawk stainless 44 Mag is $829.
A call to Ruger will get you the date it was made
Ruger's web site has a sn date function
500 or so
Ruger has sn data on their website.