My guess is this. They will get one good prospect, a mediocre one and a throw in.
They are paying all of his salary, which means Sox give up a bit more. I think it will be very similar to what they gave up for Alomar. Almonte was fringe, Ring was for real, Salvo isn't a major league caliber player.
I'd guess that it will be Diaz or something along those lines, Ginter or something along those lines and then a lesser guy, maybe Ryan Meaux (Great numbers, old for his level).