I attached a picture of how the emergancy brake system is comprised on your car from the GM parts catalog. As you can see you have two little brake shoes that fit inside the rotor hub. The hub acts like a brake drum. More than likely when you adjusted the cables the shoes moved tightly against the drum. Now this type of emergency brake system is famous for the shoes freezing in place and the backing plate and springs and hardware getting rusty, thats why most people don't use the emergency brake because they freeze. Now if the shoes are expanded you might have a problem getting the rotor off because the little brake drum usually forms a ridge on the edge and when the shoes are expanded it can become quite a pain to get the rotor off. If memory serves me correct there is a special tool to get at the adjuster to adjust the shoes. Heat is the biggest enemy of any brake system. If you heated up the little drums enough to smoke there is a possibility that the hubs got real hot and damaged either the shoes the rotors or both. You can jack the car up and try to spin the wheels by hand and see if they are dragging. I would seriously doubt you need new calipers, however SS sleeved calipers are the way to go, but remember you will need to turn your old calipers in for cores so they must be rebuildable, they are very valuable. I'd change all 4 if your going to do it and convert to DOT 5 silicone brake fluid, but thats just me. Muskeegon Brake has great deals on r/b calipers if you buy a set of 4, lifetime guarentee if I remember and free pads. Just my .02
While your in there you and have the car jacked up you might want to check your rear wheel bearings for play. It would be a shame if they heated up and snapped off the spindle and the wheel went thru the quarter panel.
