Roger, those walls will last for quite a while longer with some maintenance now. We got regular bagged mix (Sacrete-but I forget which exact variety) and did a bit every weekend. You can get a bag like one for icing a cake to squeeze the mortar into the spaces between the stones more easily.
One thing that you may want to do is to get some lolly columns in place. These will take some of the wight off the walls and can start to move things above back into place. As Tom says, it's about impossible to tell you exactly how and where to do things like that from here. If you can go in the basement and kind of visualize the stress patterns and get a feel for where things are sinking the most, put up columns with beams to spread the force. Doing this now will buy you some time to get the walls stabilized and to look around for a contractor that's familiar with this type of work. If you get really lucky, you might be able to work together with him with him doing the direction and you doing the work. Again, this might be a job for him and an experienced crew also, so find someone with a track record in your area.