If one were to need to dremel away a little bit of the edge of a board to access a component underneath of it, how damaging is that to the board being "trimmed"? The board in question has the traditional ground trace all of the way around the edge that might require a little shaving.
You can trim down the edge of a board, and trim into ground traces. It's not a big deal, provided you know exactly what you're cutting through on both sides of the board. Beware multilayer boards - most arcade boards are only double sided, but, for example, computer motherboards are four or more layers. Hold the board up to the light and see.
If you're just talking about cutting into a wide ground trace and making it narrower in one place (but still connected), no big deal. If you have to cut the trace completely, just jumper around it with wire.
One thing to be very careful of is that when you cut the board, that you don't have little overhanging flakes of copper from the cut. For example, when kludging RAM into an old computer system, I was taking 30 pin SIMMs and soldering wires from the pins on the SIMM and connecting them to the board (since suitably sized DRAM DIP chips weren't available). The SIMMs were a bit too long to fit, so I trimmed them down (only ground/power planes stuck out to the far edge of the module). On one layer, the large plane is power, an on the other, ground. By cutting it, I managed to short between power and ground with a little bent-over shard of copper. On powering up the computer, it blew out the short with a suprising puff of smoke and a pop...
So, after cutting, scrape the edge of the board with a knife to make sure you clean off any possible shorts...
-Ian