Free entrance, not very big so the visit is fairly short (20-30 minutes). Lot of historic facts, but not everything is in english (~80% is translated in english I would say).

The whole site is still undergoing restoration work but it's a massive site, and there's a fair bit to see. The tour guides are super eager to converse with you and have a lot of interesting information regarding the Palace architecture, Feng Shui, history etc. to impart if you can speak Japanese. Definitely a good half-day if you want it to be, maybe something to see on a second day in Nara. Get a stamp sheet from the first site you go to, and then collect stamps from each site in the ruins and apparently you can exchange it for a souvenir at the site information centre (which is inconveniently at a far end of the site)