ya,it's possible.After unlocking you can able to switch carriers.You can unlock your Samsung Galaxy Nexus using unlock code.If you need unlock code visit Onlinegsmunlock.com Here you can get your unlock code with simple unlock instructions via e-mail.So you can easily unlock your mobile within a day.
Yes, but if you are not eligible for an upgrade you will pay full retail for the phone. You can by a used cell phone online for cheaper add long as it's a Verizon phone and switch to that phone but also remember that of something happens with that phone Verizon isn't responsible.