Down-stream from the controller, you will need to asses the laser PSU, motor drivers, and homing / limit switches. Chances are decent that a DSP such as a Ruida could be swapped in. The more challenging parts would be retro fitting the HMI (display) and calibration of the each axis (but this isn’t that bad if you have any fabrication experience and familiarity with motion control / CNC).
Here is a link to the manual of a Ruida RDC6445G that can help you with understanding the connections.