Why would my 2006 HHR lose power start smoking

Yes it was white smoke also there was a small amount of oil on the ground, came out the intake. Once we pulled over and seen that it was hot we saw that the guage was on hot. We towed it to a friends house and the next day it still wouldnt start. It doesnt take much for the battery die before this occurred, for example leaving lights on for few mins would have to charge battery. The motor has over 200,000 miles on it. Someone says headgasket but if I have to replace that I may as well replace or rebuild motor. Have only had this vehicle since feb, never had an issue other than when I unlock it the alarm goes off.