Lots of red flags here from many angles. You had better wait until you have your commercial certificate in order to fly that sprayplane no matter who owns it. It's not hobby flying just because your uncle owns it, and it is not a farm tractor. Without a Comm license, you risk getting an FAA letter of investigation which is a career killer, or worse, if you crash you are really going to be sorry. When you do get your COMM license, fly very carefully, because spraying is one of the most dangerous forms of aerial application. If you want to do something in aerial applications now get your commercial license first, and tow some banners. Spraying is way over your head. The statistics show that <500 hour pilots are the most at risk, and spraying is one of the most dangerous activities.