You are not changing your keys, unless they have been compromised.
You are changing your recovery account.
It's been a long time since I have done it.
I have been hitting the keychain error issue and have not been able to change my recovery account, but it is straight forward.
Click recovery account, choose new recovery account, enter owner key.
But, if you hit the keychain error, it will not go through.
I really just want to change my posting key, because I'm concerned that it may have been compromised. The other keys are likely safe. If somebody out there knows my posting key, which I'm concerned about, I don't think that they could retrieve my other keys without the owner key or the master key; and I have both of those in a safe place.
Yes, the most they could do is vote for you and post things.
Your active key is required to move money.
Honestly, I wouldn't worry about a posting key, unless they did access the account.
The learning curve is steep for hive, they likely have no clue what they have, IF they have your key, nor how to use it.
But, you should change your recovery account for the off chance that somebody did find your master password/owner key.