hub assembley

I know this my be a stupid question but I'm new to the 4x4 thing so i need to ask some question. Here it goes. How do you know when you have to replace your hub assembley or half shafts? I can tell you that when I back out of a parking space my get a thuck. I steering wheel has a lot of play in it and I have a shimmy as I drive down the road.

Could be a ball joint. Here's a link that might help you learn about 4x4's http://www.pirate4x4.com/welcome1.php