The biggest issue is if you have kids or not when you come into that sorta wealth. If I had children I would feel some obligation I think to retain said wealth for them and future generations.
Since I don't have kids though I think it would be fairly easy. First a billion dollars is a heck of a lot of money. If I am still a "billionaire" after paying the taxes on the windfall than I essentially have more money then I really know what to do with.
First) I'd probably make a gift to some family members of paying off their mortgages. That will probably run me a million or so. Hopefully that would be a sufficient gesture that they would not resent my sudden wealth and be glad that my good fortune has made what is probably the biggest monthly payment in their lives a thing of the past.
I don't think I'd move or anything but I could probably drop a 100K or remodeling my own place.
I'd certain acquire some new costs like hiring out the law work etc.
I'd probably blow another few hundered K building a bigger garage and picking up four or five fun cars, nothing nuts like a super car or anything stuff I could actually drive, a Tesla, Alfa 4C, Corvette, and couple interesting classics.
I'd travel and go cool places. Invite my current friends to go with with me on my tab. Again though nice hotels, good resturants etc, but no renting out the entire floor or anything nuts.
The rest I probably just live life as I do now with, for the most part. I guess I would on my own projects like OSS stuff rather than work a day job.