Start early — 3-6 months in advance — and produce actual learning modules that meet specific learning goals and are relatively easy to manage and grade.
Redesign is an incremental process. Try not to include too many new activities at first. Start small and you can build it one step at a time.
Experiment and learn as you go.
Keep technology use simple in order to avoid turning the course into a support nightmare and gradually add more advanced technology.
Remember that as you increase significantly the number of assignments and opportunities for feedback, you also potentially increase your own work load. Don't burn yourself out!