Left posterior ethmoid mucocele w/no orbit or cranial extension but eye discomfort symptoms. surgery necessary? can/should it be delayed?

Depends: The problem is that your mucocele is likely a diagnosis from an x-ray (or some other imaging device) not a biopsy or you wouldn't be asking. Since we can't be 100% positive that it is "just a mucocele" the risk remains untended. Speak to your physician and dentist about the risk factors for cancer, cysts, etc. Seek a referral to an ent.

You can wait: Mucocele removal depends upon symptoms and position. By themselves they are not harmful, but if they press upon important structures, invade adjacent spaces or cause symptoms like bleeding or doubling of vision, then they have to be drained and removed. If you have no dysfunction, you can wait.