The car is a 1984 Firebird 305 with a 4bbl carb.

The weather here in Michigan just drop from around 60* to 30* degrees and now the damn car idles at 1900 rpm while in park and about 1100 in gear. But during the summer and fall it idle at like 900 in park and 600-700 in gear. Now that it's idling high when i shut it off it chokes for a good 2-3 minutes. Next to the carb there is a circle device that looks like it should have a tube hook to it but it doesn't could this be the problem? if i replace the O2 sensor will this fix the problem? What exactly will cause it to idle this high?? how do i fix it??

 

The choke or the fast idle cam on the carburetor.
Either take it to someone who knows how to adjust your carburetor or learn how yourself. There's a ton of info out there on the web and in the library about quads.
What you need is really simple and maybe if you find a nice mechanic he'll even show you how.

 

your choke thermostat could be shot. i had a similar problem. i replaced the ct and everything was fine again. i don't think the 02 sensor could be doing that.