maintenance, tune-up and being diligent, etc...

Hello,

just wondering how the owner’s manual outlines a regular tune-up/maintenance schedule and how militant are most people at following it?

other than regular oil / air filter changes, I haven’t really done everything to the letter of the owner’s manual.

how important is it, for example, to have the fuel filter changed every so often? or the door latched greased? or the coolant flushed?

and has anyone found it worthwhile to actually get this all done at the dealer?

i have a '98 Altima, with 138000 km’s - so it’s older but runs just fine, I think…

thanks in advance for your thoughts!