Hyundai Repair: Automatic Trans, transmission overhaul, best bet

Question
I have a 2000 Tib Automatic and it has been having trouble shift into 3rd and OD. The trans just started make a whining noise about 500 miles ago but it didnt change the performance of it.I had a flush done and hyundai trans oil was used  the noise was still there but it seemed to shift a little better,but still clunking into the gears. Tonite i stopped at a red light and then it turned green so i went like normal but it wouldnt got and was knocking and sliping so i shifted into 2nd and it was fine. I parking it and shut it off and added a little oil,before i added any i check if it was leaking,,no oil and no puddle. Drove home in drive with OD on and it was fine. Should i just buy and rebuilt on or should i have it rebuilt be a shop or the dealership? Please give me good advice and the cheaps fix.

Answer
If you haven't checked your fluid level, do that first.  If it's low, check the vehicle for leaks, not just for puddles under the car.  You'll want to visually inspect the outside of the transmission and the cooler lines as well as check the coolant to make sure transmission fluid isn't mixing with the coolant.

Next, have the engine and transmission diagnostic trouble codes read.  Depending on the trouble code, it's possible (but not likely) there's a simple solution.

Most likely, however, you'll need a transmission overhaul or replacement.  There is no cheap way to do this.  Even a used transmission will be expensive, and when doing a cost comparison, doesn't seem like a good value compared to a factory remanufactured transmission.  It's my opinion that a factory remanufactured transmission will be your best bet in this scenario, but I also think you should call some places and get price quotes and decide what's best for you personally.