How many miles on your car?
I'd just replace the bad axle... My experience w/BMW and a half dozen family Subarus here in Colorado is that they die slowly with plenty of warning and don't explode with your car bursting into flames. You'll usually here a regular clicking noise if you do slow circles with the wheel turned all the way left or right. If a boot bursts and throws grease everywhere sometimes you'll smell that if it hits anything hot under there.
If you have the car up, carefully inspect the axle boots on the other side as well as the steering boots for tears which are often hidden in the folds of the bellows. Move 'em around with your hands, pull and tug a little to find the cracks.
I stay out of the "new/rebuilt axle debate", do what you please.
Also, I wouldn't jump to replacing the 02 sensors. If a code reader gave you that, it's giving you a clue not necessarily telling you the part is bad. You may replace it and have the same code immediately. What codes did the car throw?
Steve in the foothills of the Rockies
1967 Jaguar 420G
2003 Moto Guzzi 1100
1989 Honda XR600r
1968 BSA Shooting Star
Last edited by biglittledog; 12-19-2013 at 09:46 AM.