Switching can take a while the priority with any new addition is to get the snake established first and be consistent with feeding, which mean offering the same type prey than the previous owner for at least 4 to 6 consecutive feeding

Your priority is to get the snake to eat for you first, once established you can attempt to switch your new addition to F/T however there is no guaranty that it will work so you should always be prepared to feed live if necessary, if you are not prepared for that I would recommend getting a BP that already eats F/T.

I feed over 100 live preys each month and none of my animals ever sustained any injury, when done responsibly it can be done safely. (Small rats which are generally 4 weeks old 60/75 grams do not pose much of a threat)

Feeding in the enclosure allow BP to ambush their prey from the safety of their hides which is often best.

Feeding outside the enclosure can be stressful enough to lead to refusal and you will also be more likely to get bite when feeding outside the enclosure (BP stays in feeding mode for a while and most accidents happen when the BP is placed back in the enclosure)

Whenever you handle a snake you should wash your hands before and after, if you smell like a prey you will get tag.