These kinds of questions are extremely difficult to answer, as every project is different.
This is where your budgeting needs to begin.
You are going to be doing interviews, so you'll need a camera or two, and solid production sound - lavs and a boom w/recorder. You can DIY or you can hire a crew. How far will you be traveling for the interviews? Will it require you to transport, feed and house your crew?
You want to use archival footage. Archival footage can be
very expensive depending upon what it is and the source.
Is your editor a talented up-and-comer or an experienced pro? That will affect your budget. How much material will need to be vetted? How much visual and audio clean-up is required? This can be expensive. What do you need in the way of graphics? Another variable expense. How about the score/music? Original score or canned tracks?
The list goes on and on.
There are two ways of approaching your budget; you already have a budget and will need to figure out how to shoehorn all of your requirements into the budget, or you can figure out how much everything will cost and raise the funds. But either way, you first need to figure out your requirements.
Perhaps and experienced production partner would be the way to go.