See a general practice doctor first, they will refer you to an audiologist if it's more complex than needing ears syringed (common!). If the audiologist thinks it's anything sinister or unexpected they will refer you to a specialist.

Any specialist treatment for age related hearing loss beyond a hearing aid will cost much more than a hearing aid from even the most money grabbing hearing aid sales person.

Ask your father what he wants, he probably wants to ignore it but get a hearing test anyway. They will immediately try to sell a hearing aid so be prepared to say you'll come back for that later.