Recently I noticed my 323 tends to overheat alot. (No boiling over) I took it to a mechanic and he said I have a possible blown head gasket. I have to take it to an engine shop to find out.

Can anyone tell me what ballpark price it is to replace this? thanks for the help.

dude,if any body straight tells you that its a blown head gasket dont believe them.1st check for any leaks around the motor,radiator,heater pipes.2nd check that your thermostat is workin to let the water into the motor,take it out as it cools the motor down morequicker than normal.If you dont find any problems with that then refer to the head gasket.good luck

Losing coolant? White smoke coming out of the tailpipe? Bubbling in the radiator? These are some signs of a leaking head gasket. But there are several things that can cause overheating. For instance: a thermostat that's not opening properly. And is the engine fan working? There's a coolant temperature sensor that tells it to turn on when the engine's getting too warm.
Be suspicious whenever anyone tells you it's a possible head gasket problem without doing diagnostic tests.
Find a new mechanic and get a second opinion.