Richard, Determining the damage in the interior walls is very difficult. Luckily testing equipment has been developed that can test for moisture content with no or little damage to the structure. I would recommend contracting with a company equipped and trained to handle a claim like yours. You may be concerned about the wallpaper and walls, but the overriding concern must be the potential mold problems that can occur which makes it a health risk for you and your family. Contact someone who is a member of ASCR (Association of specialists in Cleaning and Restoration) under water damage in the phonebook. There is a standard developed for handling water damage written by the IICRC (Institute of Inspection Cleaning and Restoration Certification)
Here are the Associations Web sites that can help in locating a contractor: ASCR http://www.ascr.org/index.asp IICRC http://www.iicrc.org/index.html
These companies will be able to work with you and your insurance company to handle the claim.
Because of the health risks that can occur due to the mishandling of this type of water damage I would not consider this a do it yourself job.
Hope this is helpful, Clark Seabloom Master Restorer