2003 E250 Reverse Lights Suddenly Stopped Working

Hi, I've seen this same problem all over the web, but nothing definitive as far as answers. I believe I've narrowed it down to the NSS, but have a simple question before I purchase & do the work. I've confirmed the fuses & bulbs are all fine. Replaced brand new, actually. After doing some basic continuity testing I haven't found anything to indicate anything else & it appears there isn't another reverse switch/sensor or fuse located on my vehicle besides under the dash, so again, I assume that leaves me with just the nuetral safety switch as the culprit. Question: there's nothing else that seems to be affected with my vehicle, except that my reverse lights will not turn on. Can a NSS malfunction only affect just the reverse lights? Or is this unusual & or would I see other issues like failure to start in park, etc? And I guess there are couple of more questions I have to go along with it. There isn't another reverse switch located on my '03 E250, like I've seen on some of Fords other vehicles, correct? When installing a new NSS, are there any types of adjustments needed, like to the shifter arm or NSS itself? Thank you very much for any help.