Field Updates

I believe as long as the email address is the same, it should simply update the record, and if you have the field permissions set to do so, any changes on the Marketo side will sync up to SFDC.

That being said, I'm not 100% positive on this since email isn't the unique identifier within Marketo. Hopefully someone with more experience can confirm or deny this.

Actually the email is the unique identifier for auto deduping.

If the email entered into the Form matches, yes it will update the Lead OR Contact record that matches. If there are existing duplicates/, Marketo usually chooses the most recent record.

Marketo cannot update Account records in SFDC. Only Leads or Contacts.

The real problem is that you don't want your updated info overwriting existing data on the Contact. (or maybe you do, but usually you don't). So make sure Field Blocking is enabled on key fields like
-Lead Source
-Name
-Address
-Phone

We use a landing page at tradeshows to keep notes and submit records to Marketo and of course we use the RingLead webhook to update existing records in Salesforce. We can even create new Contacts in existing Accounts and not just new Leads.  

The RL UI allows field by field selection of field actions based on the field type.  Overwrite, update if blank, do not update, append, prepend, merge (for picklists), raise, lower and increment.

We take notes at the booth, make selections from dropdowns, add to a campagin, and prevent duplicates, right there from our iPads.

Of course we scan badges, but that process is a nightmare. It is too slow and impossible with the one scanner and six people at the booth to memorialize the conversation.

We import that list later into Marketo and update the records at the booth with the landing page, again via Marketo and the RingLead webhook.

With RingLead, the emails do not need to be exact match.

If you are coming to Summit and want to see how it works, stop by the RingLead booth #226.