Transplanting to higher ground would definitely be best, but redbuds don't always transplant well.* They tend to have a taproot.* Fall after leaf drop or in spring before bud break would be best.* I think I gave you sites on how to transplant trees.
With plants it's often best to remove yellowing leaves as the leaf won't turn green again if it's time to shed the leaf.* Most arborists will tell you not to as the tree will shed them when it's ready.* You could leave a place for insect pests to invade when you remove the leaves.
Newt
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.