Amphib HQ Ferry Crossing

[ATCSLENHART]

I'm playing the Battleground Italy 43-45 scenario and I'm preparing to advance across the ferry hexes across the Strait of Messina and I understand the Amphib must occupy a Ferry hex, the combat unit move on to it and attack and if the defending unit vacates its hex by shattering, retreating or routing my combat unit can move into the hex and that if the attack fails my combat unit will retreat back to Sicily. My question is does the Amphib HQ and or the ground units need to prep for this or does the Amphib HQ simply move to the Ferry hex and the ground unit conduct its attack with no prep required? Thanks for any help on this.