You do not want to release a mainspring on a 400 day clock without the correct tools. You will lose fingers or at least brake fingers trying. Your clock probably needs a good cleaning and oiling. Look in your yellow pages for clock repair shops in your area and then ask others (watch shops, jewelers, etc.) about their reputation. Once you have found one with a good reputation take it there to have it repaired.
Stevens Clocks, October 2011
