As to a lawsuit, no doubt the cost of this course could easily be more than the cost of the refrigerator. Plus, if your purchase agreement had an inspection clause, it is possible that you could not hold the listing agent liable. If you inspected the home (either yourself or hired a home inspector) and then waived this contingency to complete the purchase, you in effect said that you have personally inspected all visible aspects of the home and approve of their quality and condition.
Start with the agent who represented you. They may have some ways to "encourage" this agent to live up to the standards of Honesty & Integrity that are the minimum for all licensed agents. If they are Realtors, you may have an ethics charge which could also hurt them, if they aren't more helpful.
As to who is at fault, I can't know. As an agent I often rely on what I'm told about things like appliances. If my seller says, "that fridge is new" I probably won't challenge them unless something overtly makes that a questionable claim. For some people, a 10 year old fridge is "new" because the old was lasted 25 years. This isn't an excuse, but an explanation of how some people interpret things.
If your agent isn't helpful, speak to the listing agent's managing broker. They are responsible for everything done by their agents. This alone may solve this quickly, but you also have the other options. Best of luck and let us know how this turns out.