Depending on which decals you use will determine how much yellow you will have to paint. All the sheets have the lettering, numbers and fuselage stripes included. Some decal sheets also include the yellow bands for the tails and wing tip, some do not. The one part that you will for sure have to paint is the wingtip missile rails - no one that I know of makes decals to cover that part.
The only modification that the Blues do to their Super Hornets are to put in a plug on the gun port and adjacent gas vents. Otherwise the aircraft are the same. The airframes are supposed to be able to be reconfigured into fully combat capable mode within a 24 hour timespan if needed.
Thank you. I think I only had to paint the wingtips & missile rails, and a few small items like the blade antennas on the fuselage, and perhaps the tips of the vertical and horizontal stabilizers.