traditional pension plan switched to cash balance account

In 1989 my company switched from a traditional pension plan to a cash balance account plan without offering its employees a choice of plans. If you weren't 50 years old or had 20 years of service you were not grandfathered under the old plan which means we lost 50% of our pension. The company never disclosed the consequences of the changeover. Is there any legal recourse -- is this grounds for a law suit. Should I be looking into suing as an individual or should I try for a class action suit? Where would I begin to look into this matter and/or find an attorney involved with this type of pension problem. The Federal government is currently investigating whether or not these conversions were illegal, but it could take years before the government makes a decision. Any suggestions on what the next step would be?