Here's my suggestion: for simple, one-off changes like this where you already know the Z-Wave parameter number, size (bytes), and your desired value, use the Basic Z-Wave Tool. It's a driver you can install under "Drivers Code" in the admin UI, then temporarily switch the device to it, make your changes (use the "Set Parameter" command in this tool and provide the three values you need), and then switch back to the regular driver. Then, you don't have to worry about a custom driver just for this (or other Z-Wave devices) when all you want to do is change a parameter. If you aren't familiar with installing/using custom code or have questions about how to use this particular tool, feel free to ask!
PS - If that's the Monoprice Z-Wave Plus PIR Motion Sensor (PID 15271), that manual is incredibly hard to find except in-box, which I have long since lost (I e-mailed their support once and they said they didn't have an electronic version). Assuming you do have an electronic copy, if there's any way you could share where you got it or upload it somewhere, lots of people--or maybe just myself--would be quite grateful. 
