Most visitors online was 1990 , on 7 Feb 2022
Suggest that you do some reading of books on basic clock repair so you will know how to proceed safely. Dealing with springs, you first need to use a letdown tool to totally unwind the spring so there is NO power left. As for removing the barrel cover, do not pry it off. I hold the barrel tight in a gloved hand then sharply whack the arbor (shaft) on the opposite end with a brass or plastic faced hammer and the cover shou pop off. You can also hold the barrel and slam the opposite end of the arbor against a block of hard wood an the cover should pop off.I've never opened a mainspring barrel. I'm not sure if its cover comes off easily or has to be pried off. I don't see any screws.