We have the Winnebago version on your coach, the 08 Vectra. I bought our replacement filter at Home Depot. The light bulb you are replacing is probably the same kind I had to replace when we were at GNR. The ones over the bathroom sink cost $.80 apiece, but the one over the kitchen sink, is an LED, was $9.00.
And that was at the customer service store at the factory. I understand you can get them cheaper elsewhere, but I haven't explored that yet. Just be sure to wear gloves when you replace the LED bulb, and DON'T touch it with your fingers or it will ruin it.