Is the battery O.K.. If it is, then remove it. Remove the pointers, they should just pull off, or there may be a small nut on the end of the spindle which the pointers fit onto. Removal of the pointers will probably reveal a brass or plastic nut which holds the mechanism to the back of the clock face, unscrew the nut whilst holding the mechanism. There may be some washers or spacers so keep these handy as you may or may not need them when fitting the new mechanism. Replacement is simply a reversal of the removal procedure. Fit a good battery, set the pointers to the correct time and away you go. Good Luck.
Janward
February 2010