I'm going to replace it as soon as I can, hopefully before summer... but wanted to know.

When I start the car after its been sitting for a day or two, it would blow white smoke out of the exhaust. Not a lot, but enough to see in the rear view mirror.
Incase I was to resell it, is this a sign of major problems? Also once in a GREAT while it will have trouble idling.

 

try a compression test.. i get avg 135 psi and i get some blow by from the valve cover cap

 

It's probably a real light blue smoke, if so it's just the valve seals. It's a common problem with the cheap factory seals they used + some milage ofcourse. Nothing major, and they can be changed w/o removing the heads using an air compressor to hold the valves shut.
If you suspect a head gasket, open the plastic coolant jug and wipe inside with your finger. If a heavy milky oily residue means your right, but just some dirt and antifreeze then don't worry.

 

The valve seals went bad on these car and would blow a little smoke on start up. Back when they were still in warranty GM had a service bulletin about it. You just have to replace the valve seals to fix it.

 

White smoke is coolant. Are you missing any coolant? If not, try do a pressurization of cooling system. If that works, do a leakdown test to see where it leaks and how much. If all else passes, change the valve stem seals. While doing that, check if the valve guides are good. If you turn the motor so #1 i at TDC, you could change the seals without air or the rope trick. When you do that, you can see if the valves wobble in the guides without them falling down the cylinder. If they are bad, take the heads off and fix that.