I would suggest you buy an inexpensive hand held meter. They are more accurate than idiot lights and will help diagnose problems. I would also suggest that you replace the bulb fixtures with LED lights. The LEDS are inexpensive and will draw 1/5 the power of similar filament bulbs. I made my own light fixtures for the LED's using a frame found at the dollar store that holds business cards. I used flat LED panels from E Bay.
You state that a fuse holder is broken in the "power inverter". I'm assuming you meant converter, the appliance that converts AC to DC and not the other way round. The converter is usually wired to a 12V distribution panel containing fuses. Replacement fuse holders are available at Radio Shack or online retailers.