Can "Send Alerts" be used without Salesforce?

I am attempting to build a sales lead nurture pipeline for our telephone sales team. I will be receiving lists of new leads that have called us for a quote each day, import them into Marketo, and they will automatically be added to a drip campaign that sends an email, waits a couple of days, sends another email, and so forth. After 6 days in this campaign, I want the sales reps to get a "send alert" that tells them to call and follow up with the lead.

Unfortunately, we can't figure out how to add the data to the "Lead Owner" or the "Account Owner" because they appear to be Salesforce-only fields. Is that true? Are there any work-arounds?

Thank you so much!

-Sarah