Locked up 2003 KTM 125 sx?

I have a 2003 KTM 125 sx. My brother drove it and locked it up, he didnt mix the 2 stroke oil with the gas...so what do i do? What I need to know is, what all do I need to buy to fix it myself. I do not want to pay someone to fix it. Does anyone know a web site that will give me the kit I need to fix this?