For the record, I am still thanking and cursing my dad for teaching me to sail!
Old boat found as a bonus in the yard... dumpster big enough to fit the hull was probably too expensive...
Yep look for a plate near the transom... probably by the tiller, it'll tell you at very least a serial number (which might also be etched into the fiberglass hull on the transom).
Sails are pricey... if it's a laser, then buying a very used sail is cheap (craigslist is your friend). If you can piece it together and it's a laser (here's a quick snapshot of a laser):
Even used it might be worth something (not much if the hull is not sound though).
Look for cracks (spider) or holes in the hull. Especially around were you put the mast. If the mast (like said 2 pieces - tubes) and boom (1 tube) exist and the hardware on it... as well as the daggerboard and rudder... then buying a used sail you might be able to unload the boat for $600-$1000. With a trailer add another $100-$500 depending on shape.
But truly, you may want to attempt sailing it! A laser is a heckuva lot of fun to sail. Don't do it when the water is 50 degrees, and don't wait for 20mph winds or more to take it out (you'll be very unhappy learning in that much wind!).