Going back to China to work in a different industry

Hi there! I just came home from a year in China, there I was an ESL teacher. I finished off my contract, got my recommendation letters, release letter and a document to show my foreign expert certificate was cancelled. After this, I got a job offer in admin and took it. Before I left china i signed a letter of intention (instead of a contract) and now the company are trying to process the invitation letter and work permit for me. However, I am the first foreigner they have hired from their home country, so I am wondering which documents I will need to give them? I have already sent them the documents previously stated, plus a medical certificate, plus passport, degree, old visa page scans. Is there anything else I need to prepare for them to be able to get the work permit from the government? Do any of those documents have to be originals or will the scans be ok?
Thanks :)