The VC for the F/A-18D (and F-117A) is aliased to the Acceleration F/A-18 VC, so there is no update available.

So to fix the missing gear when you modify the gauges yourself, make sure you include the following gauge in [VCockpit01]

gaugeXX=cs.fa18d!wload, 0, 0, 1, 1

Without it, the landing gear is missing.

Make the gauge the last gauge under [VCockpit01] and replace the XX with the next consecutive gauge number available (but you probably already knew that! )