Well, get your gear at the same time... Dirt bikes are a lot different then skate boarding or basket ball. But it can be done.
If you can get a good deal on it go for it. I'm fairly new to motocross, my first bike was a CR250, and I'm 6'2" 170lbs, been riding for 6 months and haven't "laid" it down or "crashed" it at all.
But I have a TON of respect for my bike, and it has threatened to buck me right off when I'm not paying attention. So do NOT think you can just start throwing this machine around like Chad Reed or JS7 the day you get it....