Dip stick is a fiddle however you will soon get the hang of it.
Drop the oil and bang on a new genuine Nissan oil filter at the same time.
Best not to flush the system.
Fill with the proper 5W30 fully synth fluid, 5 lts should take it to max.
You do not mention the mileage or the model of your DE or if you did I have missed it.
Only check when cold, preferably left overnight on a flat surface.
Now your crisis is only a drama, but do keep a eye on your dip stick.