So right, Lin, I was going to say it's a Jade Plant too!
It's really not looking all that bad now, the wrinkled leaves are lower down on the stems, so it looks to me as if you're already on the right track. You may have caused the wrinkled leaves by overwatering a while ago, but it's recovering because the newer leaves higher up look ok. They're pretty dark green, though. It might need a little more light. (but not direct sun!)
What I'd do is this: Buy a bag of Cactus Mix. Slide the plant carefully out of the pot and check how the roots look. You really don't need to disturb the root ball unless you see a problem. If it's soggy at the bottom and/or there are rotten looking roots, remove some of the soil and replace it with cactus mix. If it's dry and solid (like a brick) loosen up the soil around the roots with your hands. Fill that big pot half full with the rest of the cactus mix and put the plant back in there on top of that.
Keep on watering sparingly. When you do fertilize, mix the fertilizer with the water at half the strength it says on the package. If you do break off any leaves or pieces in the process, you can just stick them in some potting medium and they'll root. As Celia says, this is always a good idea, for insurance.
