The unopened cards are probably no good. They may be alright as you say they were climate controlled, but the coatings they used on the cards during that period turned into glue when in contact with each other.
As for how to evaluate it, it just takes time, if you do not know what you are doing.
From 1991-2000 is the junk era. Cards were very overproduced so they are so common today, most people just throw them away. There are some cards that are worth a lot of money, but they are very rare and hard to come by.
I would start by pulling out any names you recognize, and any cards that look different. Then go to eBay and search for the card and see what sold prices are.
Warning though, most likely what you have would maybe get you $20 from someone. Those years are just not worth the time typically unless you can look through them and instantly know what you are looking at.
