"has any one been in a casino when they changed hands and brought in new chips? what is it like?

In most cases a casino changing hands will not close to change the rack. They pick a time, say 2AM. Gaming is there to over see the change over. The new rack chips are filled to each table. Gambling is only held up a few minutes, the same as any other table fill. It might take a minute more as a "credit in" slip must be signed by the dealer and pit boss. Since the old rack is still redeemable for 120 days, it doesn't matter if the change over gets all the old ones or not.

A casino not changing hands but changing rack chips has the same procedure but does not have Gaming involved.