I have not driven the Transfagarasan Highway, but have spent quite a lot of time in Romania over the last 20 years or so.
If you are going to drive over, allow at least 20 hours of driving to get to the Romanian border. It's an easy drive, just a long way.
Romania is a fantastic Country, very friendly and welcoming with a lot of great roads to drive, especially in the northern part of the Country.
If you go, I am sure you will have a great time.
