Replacing the ball joints early is a preventative measure. They are only $30 each so it's a not big investment.

They can also be done in about 10 minutes and you will not need an alignment afterwards.

After jacking up the car and removing the wheel, you are only 4 bolts away!

If your car is from a salt area, you probably should spray down the bolts with some penetrating spray. Remove the main 18mm bolt and the 3 10mm attached to the lower a-arm.
You can push the ball joint off of the spindle with a screw driver and hammer
After removing the old ball joint, just insert the new one and bolt it up. The ball joint has a groove on the shaft where the bolt needs to sit. Line up the groove of the ball joint with the bolt and it will slip through.