Drain it yourself, put in fresh fuel with some cleaner, clear the codes and drive it.
If it comes back then maybe get it looked at. I suspect it will be fine. Worst case it might need a couple of coil packs - probably not.
Does the tank have a drain plug? With the old gas you could slowly mix the old gas with good gas and use it up. I can't believe it would be as bad as they're saying. Its not 20 years old, its 2 years old.
Harbor Freight has a code reader for $49.00, Wal-Mart has a cheap one for $20.00.