Oh and your other questions, no thre is no bottom sprocket, the chain is attached to cable in most cases with a clevis/shackle. If you broke the chain your cables should have fallen through the base. Taking the pedestal apart is easy if the screws are not corroded. Start from the top down until you get to the sproket and fish your new chain/cable up from the base and over the sproket and back down...
It is no big deal..
How the heck can you bust a 5/8ths chain?? Pseew