This is a fairly easy conversion to do and doesn't take much time. You'll need a snap press or snap pliers. I have not used snap pliers so I do not know how they work. I also used some scrap pieces of PUL.
First you'll need to remove all the old hook and loop. Carefully cut the seams using a seam ripper. Sorry for the quality of the first few images, I'll redo them next time I do a BG conversion!
Remove the hook and loop from the wings.
You can remove the laundry tabs if you'd like to. Pick out all the loose threads.
Next you'll need to measure and mark where the snaps will go. I like to measure each diaper individually instead of making a template, I find the rows of snaps end up more straight this way. I placed the snaps 1" apart.
First, find the center front of the diaper, and measure 1/2" to either side and make a mark. Then, making sure you are marking the same distance in from the front edge of the diaper, make another 3 dots on each side of the diaper front, each 1" apart. I have found the best tool for marking snap placement is a clear quilting ruler. I placed the snaps approximately 1 5/8" down from the front edge, which would be the center of where the loop was. Do not rely on the stitching holes from the loop to measure, as it is not always put on straight.
Next you'll need to measure and mark the wings. I placed the snaps 3/8" in and 1 3/8" in from the edge, and approximately 1 3/8" down. Try to place them vertically where the center of the hook and loop tabs were, but pay close attention to your placement because these stretchy tabs are often not perfectly round or the exact same size from diaper to diaper. Also, the stretchy tabs on the BumGenius 3.0 are smaller than the ones on the 2.0, so use your best judgment here.
Apply the snaps to the front of the diaper. Some prefer to use a tool to punch the hole first, some gently tap the snap press to allow the cap to poke the hole. Scrunch up the fabric and go in through the pocket opening. There is already a second layer of fabric there so you should not need to reinforce these snaps.
When applying the snaps to the wings, you'll need the PUL scraps. The stretchy tabs will run and stretch with the use of snaps, so the PUL is an extra step to prevent the snaps from ripping out. Cut pieces about 1/2" wide and 1 3/4" long, depending on how far apart you choose to put the snaps. Carefully turn the wing inside out and place the PUL in the seam where you can see that the hook and loop tabs were sewn in.
Carefully turn it right side out, holding the PUL in place. Feel for the edges of the PUL to be sure it is in place where the snap will be applied, then apply the snaps. You should not need a crossover snap, so wait until all snaps are applied to see how small the waist ends up. If you feel you need one, it would be very easy to add one on one wing.
Enjoy the snaps and forget about the worn out hook and loop!