Hello,
My name is Nick Brattoli, and I believe I could help you with your SharePoint site. I have been working with SharePoint 2010 since it was in Beta, and am a SharePoint Architect by trade. I have done many different projects, in quite a few different industries, such as healthcare, finance, oil, and once, even vehicle towing.
I would need some more information about this project to be sure, but it looks to me like you just need some external lists created, with appropriate relationships. Do these need to be writable, or are they read-only? I ask, because there is a different solution for each use case.
If you would like to further discuss this, please contact me shortly. While I do not have much experience on Freelancer.com, I have been doing this for quite some time, and believe I could help you solve your problems quickly.
Thank you for your time and consideration.
Sincerely,
Nick Brattoli