The driver transistors are welded to the heat sinks. If you place them leg side up on your bench, you can hit the bottom of the transistor case with a large screwdriver and the transistor will break free from the heatsink.
I then use a tapered reamer to slightly open up the hole in the heatsink so that a new transistor can be pushed in from the bottom. I will tack solder the new transistor's case to the heatsink.
The simplest light bulb limiter can be made from a wired lamp socket, you know the kind of socket with the wires already attached and two insulated alligator clips. Put an alligator clip on each of the two socket wires. Then use the clips to attach the bulb to the two terminals of the fuse holder, so that the light bulb replaces the blown fuse.
100 watt incandescent lamps are difficult to find, I'd just use a 60 watt one that are still being sold everywhere.