Carmack was definitely taken by surprise, though he did eventually voice approval:
http://www.theverge.com/2014/3/30/5563440/john-carmack-faceb...Facebook's acquisition of Oculus was announced only a few days before Michael Abrash publicly joined the company. Not sure when Abrash made the decision to leave Valve for Oculus. He did shine a positive light on the Facebook acquisition in his welcome post, but as you suggested it's not as if he was going to badmouth his new employer either way: https://www.oculus.com/en-us/blog/introducing-michael-abrash...
Palmer Luckey, it seems, was at the very least aware of Facebook's interest and informed of the buy-out, though it sounds like Brendan Iribe handled the business decisions.
This was the best source I could find on what went on behind the scenes between Zuckerberg and Iribe:
http://www.vanityfair.com/news/2015/09/oculus-rift-mark-zuck...
> Discussions ensued over the next few weeks, during which Facebook offered roughly $1 billion, which Iribe considered low. The deal seemed to peter out until late February, after news of the WhatsApp deal hit: Facebook had agreed to pay $19 billion for the messaging service. That got Iribe’s attention. “Hey Mark,” he wrote in an e-mail, “we should talk.”
> They agreed to meet. “Come up and see me,” Zuckerberg said, according to Iribe. “I’m not going to waste your time.”
> Iribe met with Zuckerberg for brunch on the patio at Zuckerberg’s Palo Alto home on a Sunday, in March. They ordered pizza, and Zuckerberg made a new offer: more than $2 billion in cash and stock. It was rich, considering that Oculus had not yet released a consumer product. Zuckerberg promised that Oculus would operate independently within Facebook, just as Instagram did and WhatsApp would. There would be games, sure, but eventually much more: news, sports, movies and TV, cat videos—everything. “I want to do this, and I want this to be the future of Facebook, long-term,” Zuckerberg said, but Iribe would have to act quickly and promise not to shop the deal.
> Oculus, by this point, had a board of directors that included four venture capitalists, one of whom was Andreessen. The board would have to approve the deal. Andreessen hated the idea of selling so quickly, without talking to Facebook’s competitors. “Don’t do this! Don’t do this! Don’t do this!” Iribe recalls Andreessen saying during a late-night meeting at his house after Zuckerberg’s initial offer. (In light of his role on Facebook’s board, Andreessen recused himself after Oculus’s founders began negotiations with Zuckerberg in earnest.) But the board approved the deal.
> It was sealed at Zuckerberg’s house just three days after his and Iribe’s Sunday meeting, over a dinner featuring mushroom risotto and scallops. The meal, Luckey recalls, was “so good.” And Facebook was the right fit. “I knew I was going to want to work in V.R. for the rest of my life. Anything that can make the industry big and successful … that’s a supercool world that I want to live in.”