I've got hepatoblastoma. Now what?

You probably don't. Have the diagnosis checked. Almost all hepatoblastomas are in children - most less than 3 years old. So if you are asking this question (and it is not being randomly generated by a computer) you probably don't have hepatoblastoma. Any more information?
Aggressive. Need to be aggressive with treatments (radiation and chemotherapy) and close monitoring by your hemstologist/oncologist for side effects and recurring malignancy.