Re: LED bulb replacements
You're fine with the original fuses, assuming they were sized correctly to begin with.
The fuses are sized to protect the wiring, not the device. When a fuse pops (assuming the wiring wasn't damaged in some way, causing the problem), it's because the device already cooked.
Think of the 120v breakers in your house: You can plug a 4-watt night light into a 20-amp circuit. That's quite kosher. The breaker is sized so that if you draw in excess of 20 amps (at 120v, that would be 2400 watts), it trips before the wiring overheats.
Rule of thumb for short wiring runs: 10a for 16AWG wire; 15a for 14AWG; 20a for 12AWG; 30a for 10AWG...