Certified GKH Gardening Expert
The leaf drop could be due to the plant needing a bit more water, or if the leaves have turned yellow, you may be overwatering your plant.
Transplanting should be easy. Make sure you're moving up just one or two pot sizes and that your soil mixture has plenty of drainage. This would be a good time to separate the root clump if you want to propagate the plant. If they are in the ground, just be sure you get most of the rootball, and have the new location ready before you dig it up. Also water it the day before you transplant, and after it is planted.
Here's a great article on how to care for your shrimp plant: