Mentioned in the article.

People involved:
From the SRF : King Juan Carlos and Q.Sofia, Infanta Cristina and Urdangarin and Infanta Pilar.
The articles I found never mentioned Infanta Margarita apart from the fact she received the Hernani title.
No idea how the bulk of the sale of the paintings was divided between the three siblings, but it is normal she might have received her share.

Teresa Mariátegui Arteaga, the duke's widow, accepted her role in the scam.

Sabino Fernandez Campo, chief of the Royal Household.

The then director of the Prado Museum, Alfonso Perez Sanchez.

Felipe Garín Llombart, director of the National Heritage Institute.

The Head of the Tax Authority.

The Head of the Supreme Court of Spain.


2. The story became known because the Mendez de Vigo family blew the whistle, started several judicial processes and made them so public that the RF, shamelessly, started processes against the family, with all the weight of their name and status.

Antonio Herrero of Radio COPE revealed that, late in 1994, the threat of retaliatory measures against those who might expose the scam were still in force.