2005 Hyundai Elantra put oil in transmission

Engine oil light was on as I started to take my boyfriend to the airport. Popped the hood, then opened the oil reservoir on top of the engine to add oil real quick so he didn't miss his flight. There was solidified oil, like pudding filling the opening. I asked boyfriend when he changed the oil last, (its his car) and he said "I don't know". I cleared it out the oil souffle and tried to pore oil into the reservoir, but it was clogged. I grabbed the funnel and asked boyfriend if this opening was the oil dipstick opening and he said "yes." Poured a quart in at the dipstick, found the dipstick, put it back in and it was then that I noticed the dipstick had a/t oil written on the handle. Boyfriend wanted me to still drive him to the airport! I made him call a friend to take him.

If I do a transmission fluid change, will that be enough? Maybe once I drain the fluid, I could take a quart of transmission fluid and pour it in leaving the plug out so it will flush out the system? And I'm thinking an oil change is needed too. What do you think?