300TD Harmonic Balancer

1) The H/B on my '79 300TD has spit it's retaining bolt and free wheels on the crank shaft. I'm hoping I can simply replace the shaft key and retaining bolt. Is engine balance going to be a problem? How much damage or wear is acceptable on the balancer. I believe it was loose for some time.

2) I have a very bouncy ride from the rear hydropneumatic struts. I'm told to replace the accumulators. Is that as simple as it looks? Do they need to be charged or bled before / after replacement?