Yahama WR 250 2000 Model Broken Gear Lever + Rad?

Fell off the bike over the weekend smashed the rad on the front left side and bent the gear changer, went to fix the gear changer but when I readjusted the level and went to tighten the bolt back up it didnt grip well and when I applied pressure on it, it knocked out of place, i have downward gear selection but not upward, tried getting it off but it would not come off over the bolt it was locked to, I think the teeth might be worn off inside the level, are they hard to replace, dose the bike take coolant in the rad or straight water are the rads hard to replace or is it just a matter of disconnecting the pipes and slotting a new one in, could I drive with only half a rad, would the engine just overheat