Does written contracts have to be signed to be breeched

[wpcus]

Indiana. I have a written purchase agreement signed by me for my business. The buyer called to say they wanted to wait, it has been over 1 year since all this started and had decided not to do the buy at this time. I also have a written signed (BY ME ONLY) employee contract and they have filed for a certificate to do business in my state using their busniess name and dba mine which as of today is still active. I am getting mail in their name daily. They had scheduled a meeting to fly here and sign the papers in dec. 2004 so it would all be done by year end. Meeting was rescheduled and then cancelled. I have employee handbooks that were sent, insurance packages for my employees that were sent. My business hired additional employees at their request with the promise of certain benifits that they offer employees, and took on new customers at their request. Now they have left me holding the bag on all the added expenses without coming through with the working capital that was part of the agreement. Is it wise for a very small sucessful business to sue for breech of contract and take on a very large one.