yesterday I was driving my truck home, about a 10 mile drive, and white smoke started pouring out exhaust pipe

(true dual exhaust, was only on driver's side pipe) I got the truck home, and checked the radiator, which had coolant in it, but way down towards bottom of the tank. I'm pretty sure I blew the head gasket on the driver's side. The motor ran a little warm, but not in the red on the gauge. So today, when I went out, I figured I'd fire it up, and park it on the pavement, to make the repair easier. And when I hit the key, all I got was a grinding sound. Did I lock the motor up? Any body ever go through this before? I don't want to take the time to repair the head gaskets and all the related labor if the motor is junk. My thanks in advance for any insight and help I can get.