Do you need to actually move a rocket to a factory to retool, or do you just declare it and flip a card?
Retooling flips a card in your hand, not a stack. Therefore, the position of your rocket, or even if you have one, is immaterial.
In know you can only have one black card per factory, but can you freighter a card back and sell it for WT in LEO, then take a retooling option on the next turn to immediately flip another card?
Simply put, yes. But note that when you sell a black card at LEO it returns to your hand as black. You do not need to retool unless you want a different black card.