Any "good" shop should be able to figure out real quickly if the board is edge high enough to warrant filled the gap just by handling it. You can check yourself with a true bar or some substitute instrument like a level or other precise straight edge (carpenter's square). Usually only happens if you ride your edges a lot. If your edges are always dry and free of wax, you might have a chance to be edge high.
The only way to know for sure though, is to measure.
I imagine if they stoneground the base, they'll probably fill in the gaps, too. A stonegrind is worthless if the end result isn't bringing the base back to a nice, flat surface.