I've never worked on a GR-D30U but my experience with the JVC GR-Dxxx series has produced many symptoms very simliar to what you describe. Usually caused by defective SMD capacitors throughout the unit. These capacitors are located on every circuit board in your camcorder. If you replace them all on one circuit board your camcorder will work okay for a while and then another problem will develope. I am not a JVC ASC (authorized service center), but my theory on why this occurs is that these capacitors receive DC voltage during operation and then the camcorder is put to rest for long periods of time, causing these capacitors to dry out. When unsoldering these capacitors for replacement an extreme odor is present (like a dead fish smell). The labor quotes you posted seem very fair but is it worth repair, you be the judge. Good Luck