Yes. Use a small piece of leather, cloth or even a piece of paper towel to protect the valve from plier scratches, then hold the valve body from rotating and use the wrench to unscrew the NRV head to access the valve internals. Don't use what appears to be a screw driver slot on the valve end as this can distort things.
Thank you very much guys for the info and responses. I tried the pump again today, and it seems to be working fine. The rod is no longer creeping out. Maybe the NRV just needed some time to get seated in good. I put some kerosene in the tank, and lit her up and she works great. Thank you. Willy