How do i change a mega fuse in a 2003 chevy trailblazer? Do i need to disconnect the battery first?

THE FUSE LINK TO ALTERNATOR. YOU HAVE TO DISCONNECT NEGATIVE BATTERY CABLE BUT FIRST TURN OFF RADIO BEFORE DISCONNECTING NEGATIVE BATTERY CABLE.TELL ME WHAT SIZE MEGA FUSE YOU REPLACING 40 AMP FUSE IN FUSE BOX..FORD CARRIES MEGA FUSE 175 AMP FUSE A MEGE FUSE DOES SAME JOB FUSE LINK.YOU NEED TO REPLACE FUSE LINK.FUSE LINK IS HEAVY GAUGE WIRES TWISTED TOGETHER THEN USE ROSIN CORE SOLDER AND SOLDER WIRES TOGETHER.WRAP A LOT OF ELECTRIC TAPE AROUND SOLDER WIRES TO KEEP FROM GROUNDING STARTING A ELECTRICAL FIRE. FUSE LINK LOCATED IN THE WIRE FROM THE BATTERY TO THE ALTERNATOR YOU WILL SEE WORDS FUSE LINK ON THE LINK.