Very true answer above!
There is also this link on our site here
http://www.askmehelpdesk.com/collect...ds-125212.html and subsequent links on that link that may be worth having a look at also.
Please also realize, that as far as the value of your cards, the condition of them makes a great deal of difference as to how much they are worth. Baseball card collectors get really picky about the condition of cards. Also, ultimately, your cards will only be worth what someone is going to pay for them. Price guides will give you a general idea as to the possible monetary value, though.