You can find out if it's a key date by looking it up for yourself online or in a book. Keep in mind that there could be varieties and mint errors that can change the value dramatically. As for grading the coin, it's kinda like metal detecting, it takes some time to get experience at that. If you're just looking to sell what you find, get at least three offers from local coin shops. If you don't have that many dealers in your area, you can also check similar coins on E-bay to get an idea of how yours compares. Grading generally takes into account the wear, damage, and overall eye appeal of the coin. Online sales of your coins is also a good option when it comes to sell but you need to be able to post a real good photo if you want to get any bidding action.