Genius Bar appointment - what to take with me

If you have the ORIGINAL receipt, that might also help. If it needs to be sent in for repair, they will not want ANY of the accessories. But it doesn't hurt to have them with you. Be sure to have your iPhone also, in case you need to create a backup of your watch before sending it in.

Apple doesn't usually replace the screen on Apple Watch. They offer you a like new replacement at a reduced price. Definitely have your phone with you as your Watch will need to be unpaired from your iPhone, which will create a full backup in the process. Accessories, such as charger and watch band aren't needed at all. And the advice to have your original receipt is a good one.

This link will give you an understanding of the costs --> watch Service Pricing - Apple Support

Well, if you don't have it, then you don't have it. Without the receipt, they may not be able to verify if it is still under warranty and you may end-up paying full price for the repair or replacement. Broken screens are probably not covered anyway. Good Luck.

Not sure what to advise you on that. Don't you have a receipt from whoever ao.com is?