The money is unknown at this point, but it's a one year, incentive-laden contract. Link. Another link. MLB.com link.
Update: Jim Street reports $2M in base salary with more in incentives based on appearances and attendance. The wording is poor, so I can't figure out whether the incentives are worth $2M or $4M total.
We've been talking about this nonstop for the better part of a week now, so all I have to say is this:
Welcome back, Junior. You were missed.