How are they going to get them out of the hole?

If you winch them up, you do more damage.
Is the surrounding ground strong enough to support a crane?

I saw a video, not sure if it was the one posted earlier in this thread or not, but a guy used a remote controlled helicopter to get some up close shots of the damage. Looked pretty sketchy at best. I bet it will be a while before the site has the green light to attempt any recovery efforts.

I wouldn't want to go ANYWHERE near it. There were still pockets underneath where the car was where you could tell it'll likely fall even further. Who knows where that cavern ends.

The entire site is compromised now. More than likely they will clear out the rest of the museum, find a nice storage place for the cars, then tear out the roof/ceiling to come in with a crane from outside the bldg.

Exactly the Museum will most likely be demolished.