That is a move up for riding. The 300 will get you into motorcycles to see if you like them and want to ride motorcycles. Hopefully you get to do it for fun and not transportation to work. You need time to get acquainted.
Have you taken or plan to take any motorcycle riding courses? Well worth the time. Just like on a bicycle, cars are your biggest problem for safety.
if you can find a big empty parking lot nearby for practicing would be good too if no gravel.
Welcome aboard. Best of luck getting up to speed. There are many other new riders that came here just after getting their Rebel/