Yes, you should resurface the flywheel if it is not in good shape!!! Better to not re-grind the flywheel if it doesn't need it.
It is not indicated to turn the flywheel UNLESS cracks appear, or it is not flat (worn unevenly), or the surface is burnt (heavy glazing). Guys will tell you "it is cheap insurance" to machine the flywheel clutch surface regardless, but that's not what the Datsun factory service manual says.
Wash ... in suitable cleaning solution to remove dirt and grease ... Check friction surface of flywheel and pressure plate for scoring or roughness. Slight roughness may be smoothed by using fine emery cloth. If surface is deeply scored or grooved, the part should be replaced.
- 1980 B310 service manual
If it is warped, have it resurfaced. It is it burnt, chattered, or is grooved, resurfacing is called for. But it if still worked great, is flat, and not burnt, don't bother. The Nissan factory service manual does not recommend a resurface unless needed. Every time my Datsun flywheel did not look great, I should have resurfaced it. And everytime it looked great and I didn't resurface it, all was fine.