Are over-the-counter medications viable for relieving fever symptoms associated with mono?

Yes. Yes, i typically recommend Ibuprofen or tylenol (acetaminophen) to use only if needed. If someone has liver, spleen, kidney or blood disorders, this may limit their use.
Tylenol (acetaminophen) Tylenol (acetaminophen) should help, however if your symptoms are not intolerable, might be best to allow the viral infection to run its course.