BUY A BECKETT!!!!
If you have what is a "set" which it sounds like they aren't worth much.
That is just a set of the regular cards. The big money is in the inserts and most "sets" don't inlcude inserts since they are rarer.
Right now is just as a good of a time as any to sell sports cards..I have been collecting them for over 20 years and while they are not as hot right now as they used to be 10 years ago, they are not as bad as say a ebie baby or something like that. Sports cards are still a HUGE business.
But like I said a full set of regular cards is not going to get you much money. back in the 80's and early 90's these sets were selling for around $50 or so and you would be lucky to get half of that anywhere. Unless of course it is a coveted year (Griffey, Bonds, McGwire rookie, etc...)
If you have insert cards then you will make a decent anount of cash.
Now if what you have is not "sets" and actually just a long ctorage box of single cards...then yes you will have to go through a beckett and price each card individually.
Now again don't expect much. Even a card worth $100.00 in the book will only sell for no more than $40.00. If you try selling that to a card store they will probably only offer $20.00 or so depending on if you want cash or store credit.
If you have a nice exspenvie collection of individuals and inserts your best bet would be to even look for a local card show and buy a table to sell them at. You will be able to sell them for a little more than normal, but again, it would be nowhere near book price what you get back.
If you can pm a list if they are full sets and I will get you the prices so you don't have to sell out the $7 bucks for a beckett.
if they are individual cards youcan send me a few to price if you want. I will need card comp (topps, donruss, upper deck, etc), Card year, card number.