If I understood correctly you're currently using the Arduino to let your cRIO (I assume this means compactRIO from National Instruments) communicate with a controlling PC. What's the current communication channel between the cRIO and the Arduino? UART? CAN?
Do you intend to replace the cRIO or do you wanna keep it and use the Arduino just for communication?
You've written you already own a WiFi shield. Which one is that? Do you also have a CAN shield/breakout? If yes, what type is it?
What's your plan for the final communication "protocol"? Sending some control commands from the PC to the Arduino which sends them to the cRIO? Has the Arduino to control other hardware directly using the CAN bus?