Q: Sluggish acceleration, excessive gas usage, transmission not shifting properly and real heavy exhaust smoking??? Repair costs???

If the exhaust has been smoking heavily for some time, a plugged catalytic converter would possibly account for at least some of the difficulty you are describing. But, that diagnosis is speculative. You could do a quick check on intake manifold vacuum. If vacuum is "low", below spec, that can indicate too much exhaust back pressure. A more reliable test is to measure back pressure ahead of the converter. If the exhaust smoke is a shade of blue, the engine is burning oil which, if due to faulty valve stem seals, is readily fixable. If the oil is leaking past the rings, though, obviously the engine has to be rebuilt. If the smoke is black, too much fuel is being delivered. Transmission shift problems can be caused by simple faults (such as a plugged filter in the pan, bad shift solenoid or faulty TPS) but shift problems can also be due to serious problems requiring a rebuild. To cover the possibility that your car can be repaired economically, that is the repairs are not that complicated or involved, you can request an engine diagnostic - rough running/smoke and the responding certified mechanic will let you know what will be required to get the vehicle into reasonably good running condition. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.