1. While creating an opportunity, the Contact (lookup field on the form to contact) and/or Account (lookup field on the form to account) can be set. In either cases, these values are stored in Potential Customer (customerid) field in dynamics. This field does not show up on the opportunity form, but can be added from settings. This field can contain only 1 value - either contact or account. See http://riics.com/main/relationship-between-opportunity-to-account-or-contact-records/ for more information. In this case, Marketo does the following:
2. Through Stakeholders : Dynamics uses connections to connect opportunity to contact through stakeholders from the opportunity create page. For this we will create an opportunitycontactrole record for every new stakeholder.