Where to begin? Membership, maps, multiple blogs, downloads OH MY.

Just signed up for WPMU in the hopes that it will allow me to create the site I want. I am impressed so far! Overwhelmed with my options would be more truthful. From what I have read I think it can be done. Can I describe what I want to do and maybe get some feedback on the best way to do it? I also have gravity forms to use.

1.Main site will display posts submitted by users.

1.1.Main page to aggregate user submitted maps.

1.2.Users can comment and vote on map submissions

1.3.Downloads to be added eventually to each main blog map post

1.4.Map submissions will create a post.

1.4.1.Submissions will have a form to be filled out. Forms will create most of content for each post to include checkboxes, a user submitted map location, and other various info.

2.Different levels of users

2.1.User level 1 can read some content

2.2.User level 2 can submit public content, read some content

2.3.User level 3 can submit public content, read all content.

2.4.User level 4 can create and edit 1 subdomain blog, submit public content, read all content.

3.Calendar

3.1.User level 1 can read. User level 2-4 can submit

3.2.Segregate calendar content by category or other means.

3.3.Main page or calendar page to aggregate all calendar items.

3.3.1.Would be nice to be able to aggregate calendar items by region

4.User profiles

4.1.Profiles will track user submissions.

4.2.Profiles will be able to track what other submissions the user has selected to be grouped with and display the groups.

I guess I am not really looking for a step by step. I can figure that out or will ask elsewhere. A best practices or methods you have found to accomplish similar would be great. Use of specific plugins and design tips would be great too. For example buddy press or membership plugin.

I know its a lot to ask. As I said I am overwhelmed and need to pare this down into manageable chunks to accomplish.