Yes

The typical set-up is that the controller box that comes with a machine is just basic motor controllers it has no intelligence. The PC using something like Mach 3 software is directly controlling the machine by sending pulses over the parallel port to cause the motor to step. As you have probably read on here this can be problematic for so many reasons but mainly because a PC running a multitasking OS has issues of latency where sometimes it can miss a step because the machine is preoccupied doing something else like re-drawing the image on the screen instead of sending the pulse.

The smoothie board has its own ARM microprocessor that does all the controlling work making the PC redundant. Because the processor is dedicated to controlling the machine it doesn't suffer from the problems a PC controller would. There are 3 ways you can load the Gcode onto the smoothie board...

Save the gcode file on an SD card on your pc and then take it and slot that in the smoothie board.

Attach a USB cable and load the file onto it that way, the best thing is that you can then use the computer for other things or even shut it down as it is not needed once the file is transferred.

Alternatively if you get one with a network interface you can load the files remotely from any computer on your network.

I wouldn't bother asking for a discount from stepmores for removing the controller as the box contains a power supply to power the stepper motors and the VFD speed controller for the spindle. So the actual controller boar inside the box is probably only worth $30 or something.