Is the new earth already built in heaven?

No. That will come at the end of time, as 2 Peter 3:10-13 says. The present earth and heavens are going to be destroyed and become a distant memory, thank God, and then God will create a new heaven and a new earth. Unlike the first creation, it will not take six days; it will be instantaneous, everything all at once. And when that happens, the devil and his minions are sent to hell, the souls in purgatory are released, and, as Paul says in 1 Corinthians 15, you will receive your new body when Jesus comes back, in the twinkling of an eye.