10 Watt is used in parallel with the light, not in series.
I should have added this. You are planning on a volt meter so you don't really need the light. The resistor by itself will do the job. I don't know if you have said what you would be using for an instrumemt panel. If the panel doesn't have a provision for the light and it will be too difficult to add, then you may want to go with just the resistor.
I personally like the light in addition to a gauge. It will catch your eye sooner than a slight change on a gauge.
