1996 Chevy cavalier Over heats smells like exhaust coming from coolant reservoir any suggestions ?

It sounds like a head gasket failure or a possible cracked cylinder head.
The engine combustion exhaust gasses are leaking into the coolent system and causing the overheating.
Have you noticed a loss of coolent with no apparent leaks?

Try taking the coolent header tank cap off and placing your hand over it creating a seal. If after a few seconds you feel pressure building and when lifting your hand slightly you'll hear the pressure release as a hiss confirming either of the two I mentioned.
Only do this if the temperature is low or you could burn your hand.
If the engine has overheated badly it could of warped the head needing it to be skimmed if it's aluminium. Likewise if the engine block is aluminium also but them two are only likely if you cooked the engine so I would say firstly it's a failed head gasket.
I hope this helps you out.
Gary