Computers are not like cars. They don't get tune ups or regular service by their manufacturers.
If there is something specifically wrong, Apple may look at it and fix it.
If there is nothing really wrong, but maybe its just running a bit slow, then post an Etrecheck report, and someone here may be able to help you get it working o.k again.
click here ➜ Using EtreCheck - Apple Community
Outside if that, any assessment of weather something is worth doing, would require knowing what needs to be done. Tell us exactly what's wrong, or what you thing Apple can do, and maybe we can tell you if its worth it.
But yes, at almost 9 years old, it may be time to consider a new computer regardless of what is wrong.