Workflow Suggestion

Was hoping someone could give me some advice on how to create a workflow that does the following.

When Lead is created , triggers an email template to Lead, then sets task to follow up phone call in 3 days. After phone call, triggers a series of spaced out emails over about 3 weeks, or until the Lead is converted.

I'm pretty new at this and I've read all the instructions, but I can only get it to trigger tasks, but I don't know how to get it to do the timed emails.

Any help would be appreciated.

Thanks