That means a contract you made before your death about how to bury and manage your funeral.
For good ---> it is not really "for good"
It means "For a long time without essential change"
Ouch! That reminds me of the famous words of Mark Twain upon reading his own obituary. ("the report of my death was an exaggeration" more commonly paraphrased as "the reports of my death are greatly exaggerated.")