pull the switch panel out from underneath the clock , then look in the gap you see 2 spring clips holding the clock in , pull them to one side and yank clock out , mine took a bit of effort but will come
I did have a link on how to do it but i can't find it.
I used two pieces of metal credit card size that fit down the sides of the clock and you then just pull it out. The lugs are 2/3" down. Hope that helps