I found this thread from a couple years back about migrating from MSD to SF: Migrating from Dynamics CRM to Salesforce
We're not using Dynamics, but are considering migrating from a home-grown CRM to SF. Our internal CRM is synced with Marketo via API calls and generally only writes to custom objects. Has anyone had any experience with this type of migration?
There are some threads on custom CRMs. Since you aren't on SFDC yet, the biggest part is to build out what you want in SFDC and the changes you may need to make in Marketo.
This is a good time to ensure SFDC is built to handle lead lifecycle processes correctly.
You will have some issues mapping fields between systems, so be ready for that.
You may want to design it all and then connect a NEW instance of Marketo to the new SFDC, then migrate your data over properly. Marketo will help here, although there are limitations on what data can be moved.
We are involved in a similar project right now, but it's a migration from SFDC to a new instance of SFDC. Marketo has recommended migrating to a new instance of Marketo for the new SFDC due to all sorts of issues, but if everything you've done so far is via the API hopefully it will be easier. Migrating to a new Marketo means losing all the current marketing activity and has it's own problems as well (losing known visitors on website, they will have a new munchkinId, how do you handle people mid nurture stream without resetting them, and so on).
Thank you both. Knowing our situation I don't think I'll get the OK to migrate to a new Marketo instance.
I think the toughest part will be figuring out how to assign the correct deal information to the leads based on our internal CRM integration and still linking them up correctly between Marketo and SFDC. At this point I'm just planning on spending a ton of time on data cleanup and deduping post-migration. Not ideal.
So I would definitely load up SF first and keep the integration off until it is populated with everything (opportunities, accounts, contacts, leads). I don't think you can update the SF Id yourself in Marketo, but it would be worth checking with Marketo if you could set this manually initially to prevent duplicates from coming in when you turn on the SF sync.
Alternatively, you could run a mass merging in Marketo after the SF sync is turned on for the first time.