"Stress" cracks
You need to determine if these cracks are just cracks in the gelcoat or are they in the fiberglass below it too. Definately don't go drilling anything until you know for sure it's the fiberglass that is cracked.
If you sail your boat much at all, you will get cracks in your gelcoat. All that is, is a sign that the fiberglass was flexing there. fiberglass has unbeleavable flexing capability but gelcoat does not.
gelcoat is basically polyester resin. Resin is used with fiberglass to create the "fiberglass" that we know of. The resin brings the compression strength which fiberglass has none of. Fiberglass brings the tensile strength which resin doesn't have much of. I guess you can now understand that if the glass is layed correctly (not much resin) then it will be very flexible and also light (I bet all the glass in your boat only weights 50 lbs...it's the resin that weights so much), but because the gelcoat is nothing but resin, then it's not going to flex much, so when the boat does flex, you get the cracks.
In otherwords, if it doesn't look like the crack goes into the glass, I wouldn't worry about it, so just chip or grind off a little piece of gelcoat on the crack and examine the fiberglass. If you don't see a crack in the glass, just cover the crack with gelcoat, sand, wax and go about drinking a beer.