When you renew a certificate, you have the option of using the existing key set or creating a new key set. If you use the same key set, the certificate should continue to work with your partners. The following link should provide some insight.
http://technet.microsoft.com/en-us/library/cc738405(v=ws.10).aspx
David Downing... If this answers your question, please Mark as the Answer. If this post is helpful, please vote as helpful.