For the carve gybe what you do is you unhook from the harness, move you back hand back, head a bit downwind and step out of the back footstrap and you put it next to the front foot. Then you lever against the footstrap with the front foot to carve the board into the curve. You really need to lean into the curve with your body. It should be paralell to the mast. When you are turning you should keep your back hand close to you. Keep your eyes(and the head) at the exit, DON'T LOOK DOWN. When you flip the rig, two things are very important: first you put your front hand as forward as you can, very close to the mast. Then let go with the back hand and grab the other side of the boom just in front of your harness lines (if they are correctly positioned). While you're flipping the rig try to be leaned into the curve so the board keeps turning. Why you need to grab on the other side of the boom so far back is because you will keep the power in your sail and you wont fall in the water like you would if you would grab the mast. This will ensure you a planing exit if you do it right. The foot change.. that i can't tell you much about do it when you feel like it. some do it before the rig flip, some after. BUT you must keep pressing the downwind rail so the board keeps turning.
Now here is how you do a duck jibe: i think the duck jibe is easier than the carve gybe. The entrance is the same. Back hand back, off the harness, back foot out, head a LITTLE downwind. When you start carving the board, you need to time your ducking just right. In time you will get the feeling, until then you will experience some spectacular flights over the nose of the board. So you grab as far up the boom with the front hand and rip the sail REALLY FAST past your ear and hold the sail on the other side somewhere around the harness lines. Remember to keep the board carving the whole time. When you hold the new side of the boom you are still standing in switch stance, so you switch your feet then. If you still have enough speed you can step right back into the footsraps and keep on planing.
Have fun and let me now how you're getting on.