Well, I'm not an expert but I did find some stuff out.
For value of historic stamps, I found a nice organized guide:
It is an estimate of stamp values from historic USA collected from various auctions and dealers. P.S. I don't think the stamps are worth much unless you have like stamps from like 1800's to the early 1900's. I find that mint condition stamps are around 2-10x higher
You can sell them on the world's most largest bidding and auction site: EBAY