I did both inner and outer with BMW parts. I figured it was not much more work... You can get them from ESC Tuning. I found the oem parts to be of much higher quality. I would also replace the axle nut. I found the you really do need an impact gun to get the axle nut off. The special tools might include the snap ring pliers and cv boot clamp pliers(the tool that tightens down the metal rings that hold the boots to the shaft).

Part numbers
31-60-7-507-402
31-60-7-565-315

Have Fun!