At present, (July 2013) sections of the tomb are cordoned off with rather ugly safety barriers, and there are notices claiming work to restore and make safe will commence in June 2013(!). While I found the distraction minor, but annoying, others may find that they spoil the experience.
Cost is now £7.00, though I suspect you could get away with just walking up to the sites. However, although before I went I thought the cost seemed steep, you get two useful introductory talks, and the opportunity to handle original artefacts from the excavation, as well as the small museum. Certainly the talk on the burned mound made visiting the site much more interesting.