Todd, there are a couple sf-Sage 100 integrations out there now. There are decent reasons for Sage customers to use Sage 100 over sf, but integration is probably not a good one.
I do think it would be a good idea to take Peter up on his offer to talk to prospect. Depending on the prospect's size and needs, you could conceivably pass the cost of the lead customization into your support agreement with them, or look at it as a cost of selling.