Marketo Governance Doc

I don't have a specific format created but yea here are few points which you should include:

• Document your migration goals
• Identify folks from different team who all are going to work with you on migration (Project manager, IT team, CRM admin, Marketo expert)
• Choose a CNAME
• Decide folder naming conventions

Then create a checklist for migration which should include following:

• Database clean up (duplicates, invalid leads etc.)
• Documentation: 
  1. Identify and document active campaigns/programs which need to be moved
  2. Templates and assets that are required
  3.  URLs of LPs
  4. Redirects to existing LPs
  5. Lead scoring program and logic
  6. Images, PDFs or other documents
  7. Smart lists and lists
  8. Suppression logic
  9. User names and roles
  10. Unsubscribes
• Set up your instance:
  1. Add admin users and support contacts
  2. Setup domains and cookies
  3. Set up email deliverability (SPF/DKIM)
  4. Sync CRM
  5. Populate leads
  6. Build folder structure
  7. Build templates and assets etc

Hope this will help you in creating a document for you and help in migration as well.