The Nissan Altima from the late nineties into the first decade of 2000 used the same basic procedure for removal and replacement of the constant velocity drive axle shaft. The shafts must provide the driving force for the front wheels in addition to flexing to allow the the suspension to move. It is simpler and quicker to replace the complete shaft if a CV joint fails. A do-it-yourselfer runs a risk of getting dirt in the joints and contaminating them when trying to replace the joints alone, which will cause them to fail prematurely. It will take you about 2 hours to replace both axle shafts.
Jack up the front of the vehicle, and support it with jack stands for safety. Place wheel blocks around the rear wheels. Remove the wheel nuts on both front wheels, and remove both wheel and tire assemblies. Start on the left side of the vehicle. Have a helper hold the brake pedal for you while you remove the wheel bearing lock nut. Loosen the nut with a long half-inch drive ratchet handle or breaker bar. You do not need to disconnect the brake caliper, but do not stretch or put strain on the brake hoses when you are moving components around.
Remove the wheel speed sensor for the anti-lock brakes if the vehicle has them. Unbolt and remove the brake hose clip. Remove the lower strut mounting bolts that connect the strut to the knuckle. This will allow the knuckle and hub assembly to fold outward. As you move the hub and bearing assembly, tap the center of the axle shaft that protrudes through the center of the hub to free it from the knuckle. If you cannot remove it by light to moderate tapping with the hammer, you may need to use a slide hammer puller.
Loosen and remove the support bearing bolts from under the car that secure the inner part of the axle shaft. Pull the left drive axle out of the transaxle. Insert a punch into the transaxle opening for the left drive axle and place it in contact with the right drive axle. Strike the punch with the hammer until the the right shaft comes loose from the transaxle. Pull the axle shaft towards the left side of the vehicle, and remove it.
Inspect the axle shafts for cracks or rips on the CV joint boots. Also, check for grease leaking from the boots. If you notice any issues, replace the axle shaft. Also, check the joints for rattles or rough movement as you flex them. Replace the shaft or joints if you notice any problems with joint movement.
Reverse the procedure for installation of the drive shafts. Be certain that the circular clips on the end of the axle shafts are installed correctly. If you can slide the shafts out of the transaxle easily, they are not engaged correctly.
