Please, please, please, please, please. At the VERY LEAST use a respirator/goggles when you start sanding. The fumes of resin? eh, it's bad but short lived if you don't breathe it all the time. But DO NOT get the dust from sanding fiberglass/resin in your lungs/eyes. That will seriously be the end of good times.
You ever see those people who fiberglass and sand boats? They wear masks for a reason. The particles from sanding are much much worse than from just glooping on the resin. They are so fine. I got plenty of shards along my arms which, while not too dangerous, hurts like a bitch for a while until they come out. I also got a tiny fragment of hardened fiberglass in my eye. Hell for a few hours until I got it out and put my goggles on.
This stuff is serious, no joking matter. If you can't afford one, save up and buy one. Ask your parents, seriously get SOMETHING on your face.