... the problem I have having is the dimensions listed for the main sail do not match my main sail.
How far off are they? Could it be that the main is just old and stretched-out?
How do I know if I need a genoa or jib?
argue you need both
A "jib" is a foresail that's 100% or smaller, and a genoa is a foresail that's greater than 100%. "100% of what?," you might ask. Well, 100% of the distance from the tack of the sail to the mast of the boat. If the foot reaches just to the mast: It's a 100%, aka: "Working jib", aka: a #3. Your largest foresail, most commonly 150-155%, would be a #1 genoa. If you have a #2 genny, it'll usually be in the range of 125-135%.
Sometimes people have bigger #1s, in the vicinity of 160%, up to even 175%. (Those are called "deck sweepers.")
A #4 jib will usually be in the vicinity of 75-80%. Lastly comes the storm jib, usually at about 25%.
Most boats make do with a #1 and #3.
We ended-up with four
#1s. I'm going to see if one of them can be cut down to a #2, or possibly even a racing #3.