“Its an old metal flat with a toe clip.”
Good brand?
“Are these worth servicing?”
Generally yes, if decent quality and surfaces not badly/unevenly worn.
“or will it just be too fiddly/time consuming?”
That depends...
Make sure you use the right size of balls. Occasionally pedals have different nunbers on each side (of both pedals not L&R pedals!).
As with loose bearings generally, right number is ‘as many as fit leaving about 1/2 ball gap’.
If unsure, put in smear of grease - enough to hold the balls - so that you can see them all - then add rest of grease.
Biggest pain is ‘losing’ a slightly sticky ball down barrel of pedal.
Enjoy.
A well adjusted pedal turning smoothly in your hands is very satisfying.
(Though it won’t spin so nicely with the toe clip attached.)