KMAIL & storing mails unencrypted

Hi all! I just ran into aninteresting problem: When a key gets revoked, then mails are not readable any more. How do I change the keys of my gpg encoded mails when I changed my gpg key, so that I can still read the mails? And as an interim solution, is it possibe to replace the encrypted part of the mails with the decrypted part or reencrypted part? Nik -- Please do not email me anything that you are not comfortable also sharing with the NSA, CIA ...