The current bell should be fine, however some older bells (ie solonoid based) will damage newer system. However id assume as you had an optima before that it is a modern type sounder and as such should be fine.
No the unit does not come with a battery, and only a 2.1-2.3 A/h will phsically fit inside the control panel.
It wires the same as the old optima, its a double pole based system so will wire identically.
Support