2000 Pontiac Grand Prix CV Joint Bad?

Shakes or Wobbles problem
2000 Pontiac Grand Prix 6 cyl Automatic 185000 miles

My car shakes pretty bad, especially at higher speeds. When I get up to about 70, the shaking is really obnoxious, but when I let the car coast, the shaking goes away. Also, when I make a sharp turn I hear a grinding noise. And, when going at very low speeds, like in a parking lot, I sometimes hear a knocking.

The tires only have about 10,000 miles on them.

Is this a bad CV joint? If so, what am I looking at (ballpark figure) for repair costs? The car is old and I don't want to spend too much on it. However, if it is a fix for a couple of hundred bucks, then I don't mind fixing it as the car is great and I don't want to buy a new one.