You will need to make your queue transactional and then set the exactlyOnce property on the binding to true.
This should take care of it. You can have multiple readers (WCF Services) reading from the same queue. That's basically a load-levelling concept and is the intent of queue-based messaging. Here is some background documentation on WCF and MSMQ.
http://msdn.microsoft.com/en-us/library/ms789048(v=vs.110).aspx