It is definitely a good idea to clean all the parts from the chaincase and give them a good inspection while changing the drive axle bearing on the speedo drive side. Changing the chaincase oil every season is never good enough. There is a fair amount of metal particle sludge that accumulates over time in the bottom of the chaincase. I would replace the chaincase seals, fairly inexpensive and good insurance. Refill the chaincase with a synthetic gear oil or chaincase lube.
When you replace the drive axle bearing, polish the drive axle with some emery cloth and apply some anti-sieze compound to the shaft prior to putting the new bearing back. the anti-sieze compound will make the bearing easier to remove. I remove this bearing after every 800 to 100 miles, remove the seals and clean out the old grease and water. repack it with a synthetic grease and reinstall it. This regular maintenance will allow this bearing to live for many years.