My def tank is full light wouldn’t go off now car won’t start can I replace the cluster

This is far too complex to guess at in this forum. You need to perform testing. Too many possible causes. Can't even guess why the cluster would need to be replaced. You say it was replaced days ago? By whom? By your approval? For what cause? Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops