Odoo Data Migration Problem

We’ve installed Odoo v8 stable release. The CRM Modules differs so much, that we can’t just export import

the database automatically. 

I hired 2 developers aleady to try the database export import, but it does not work. 

Now we try to export import partially. I began with the users. This really works. But the overview for exporting these database entities is really confusing (I mean the export panel when you navigate to the list view of the following):

• Customers
• Opportunities
• Projects
• Tasks

these 4  are very important. We have a lot of customers inserted into the old Odoo version. And now when I export import I either get too many records in the new system or I get too less information (email missing or whatever). that is because the “Export Data” panel is SO CONFUSING, I would need hours to decide what to transfer. 

But in short. We need the following entries in our new Version without loosing data:

• Customers
• Opportunities
• Projects
• Tasks

Do you have a list of what fields to add to the right export column for one of these entities (for example for customers). Or do you have a roadmap about what entities to export first (for example I can uydnerstand that I can not transfer opportunities before exporting customers because it’s dependent. Are there more dependencies)? 

Thanks for helping