Updating electrical service
It is OK to change out a 100 amp fuse panel with a 100 amp circuit breaker panel. An electrical service is measured in amps with the standards being 100, 150 and 200 for a typical home.
Just because the service is changing to circuit breakers does not mean the amperage coming in to the house must be increased to 200 amps. Amperage is like the size of the water pipe that feeds a residence - the bigger the pipe the more water that can be delivered.
Branch circuit requirements start at 15 amps and can go as large as required by the specific item and voltage.
When a 20 amp fuse is inserted where a 15 amp was the current carrying capacity of the circuit is increased by 33% without any regard to the wire size.
Remember that the fuse is rated according to the wire size that is worth repeating a little louder THE FUSE IS RATED ACCORDING TO THE WIRE SIZE.
Any circuit breaker or fuse that trips does so because the circuit amperage exceeds the circuit breaker or fuse size.
Changing from fuses to circuit breakers will increase the value of the home and eliminate the hazard of installing oversize fuses.