Well my old Sunfire, which is now my brothers sunfire is at 135,000 miles and its having overheating issues. The low coolant light is on and the temperature gauge rises almost to the top in a matter of minutes. Problem is its not low on coolant, in fact its full! Anyone got any suggestions?

btw incase your wondering its a 2200 OHV 4 banger

That 'low coolant' sensor is in the bottom of the reservoir tank, and is prone to sticking sometimes. A light whack may suffice to get it to normal. Check the burp bolts to see if there's any trapped air in the system. Did you have the cooling system serviced at 100K miles? Some shops now have a good machine that does a clean flush and fill in about an hour for a little more that $100 -- a good deal in my book.

I suggested that to my parents acctually. Anyway it's not just a sticking sensor because the engine acctually does over heat. The temp guage rises quickly and within a couple of minutes the car will start smoking. Were also suspecting it might be a thermistat... Anyone think that could possibly be the problem?

i would say that you probably have either a) air in the system or b) bad thermostat or c) all of the above.