Does anyone have experience with PIC built in camparators?

I have a few questions?

1. What max voltage can a comparator input take? I would like to input 12volts? Or will this smoke the PIC? (Alternatives if this is the case??)

2. How good is the built-in voltage reference Vref?

3. Is it better to sacrifice an input and set your own external Vref?

Cheers