Begin with the end result in mind, then start listing tasks you'll need to do in order to achieve that end goal.
Once you've listed each task, you can then begin prioritizing what needs to be done first, next, etc.
You can then create a timeline checklist to complete each task on it's own thereby hopefully avoiding feeling overwhelmed by the over-all goal in the process. Instead, you'll feel peace by being prepared and mostly likely won't feel completely frazzled by the time the actual event finally takes place.
I designed a fun timeline checklist to utilize when planning annual parties for my two boys who both have May birthdays: