If I was looking to do this project on the cheap, I would look for things that already do the motion that you require.
For example a drill press table travels up a pole (using a rack and pinion), and also can swing around the pole.
So you could buy something like this
http://www.harborfreight.com/16-spee...ess-43378.html
Stick a low rpm high torque motor on the lifting crank, and then drive a firction wheel on the horizontal surface of the column to rotate.
If you wanted to separate the 2 mechanisms i would move away from a pole and use drawer slides on a vertical frame, and then pivot the frame at the bottom like a turret using a lazy Susan bearing.
Without knowing the specs of your tv/system it is hard to recommend a motor. On the cheap side of things I will echo finding something at
http://www.surpluscenter.com/electric.asp on the expensive side you can find something exactly speced for your project at
http://www.grainger.com