Not all door locks work with remote

[mmshibumi]

Does anyone have a solution to this problem? My door locks partially work when I hit the remote button. Is there a part that needs to be replaced in all the doors? Is it difficult to replace yourself? Do you need a special tool to remove the inside part of the door? Is there a manual to describe this procedure? It seems my once reliable Ford is going down hill. Thanks to all that responded to my overdrive button that kept blinking.