I sincerely doubt that their background check will be a big problem. I've worked for one of the national labs and know what a "real" background check is like. I have done the background check for two companies that I do on site inspections for and asked for a copy from one of the companies. I was amazed at the report I received as it was basically someone just googled my name.
The bummer is going through a background check is mandatory! This sounds like a pain... Also, an I-9 is required, and is due within 24 hours.
The I9 is required by Interactions for the merger. You have to complete the form and have someone else sign it, saying you are you. It cannot be someone in your immediate family either, meaning you have to get a neighbor or friend. I forgot if co-workers are okay are not.