maint./prevent. maint

My 81 300SD is due for some maint. work.

With 315.000 km and no service record (or manual) should I be looking at replacing nozzles?
Lately, after about an hours highway driving, there appears to be some rough idling when pulling to a stop.

Had the valves set when I bought the car
at about 287.000km.

Any input is appreciated.

Enjoying this forum a lot
Cheers