1972 Front Disc Brake Conversion

Gonna have to know more information about your car. What size drum brakes are on it now? Do you want to keep the 5x4” bolt pattern it has now? Do you want to keep your current wheels, and what are they?

As for the rest of it
1- No, not necessarily
2- Not necessarily
3- No, not at all
4- really depends on the bolt pattern and what wheels you have/want