The dust could be left over from the shop repair. One would think they would wipe it down, but obviously
they did not.
What construction is your GO 171?
The higher end boards (lighter in weight) do not have a shiny finish on the bottom as a shiny finish is not
fast. It does not "wet out" to provide good laminar water flow like the "sanded" dull finish.
As far as the footstraps, you need to take a fender washer (same size as the K9 lock plate diameter)
and "compress" the sharp points on the top of the K9 lock up into the webbing of the footstrap.
If you have the longer (32 mm) 7 mm footstrap screws (what year model is your board....check the digits in the serial number) you need to use a 6mm footstrap screw to "pre-tap" the holes you will be using.
Use a bar of bath soap as a lubricant, and be sure to use a #3 Phillips screwdriver (do not use power tools at all!!!!).
After you compress the K9 locks and pre tap the footstrap inserts, you should be able to get the 7 mm x 32 mm screws to go into the inserts pretty easily if you lube them liberally with soap.'
Take the screw and rub it across the soap to get the soap to cling to the threads, then install the screw in your board.
Be sure to close the vent screw before you hit the water!