Yes, if you still have decent pressure, you can use that kit, as long as you make sure you don't over fill it. But if you have no pressure, you should vacuum the system down, and see if it holds, if it doesn't you will need to pressurize the system with nitrogen, (or something..) and check for leaks with soap bubbles. Usually it's the seal on the compressor.
If it is just low on freon, grab a freon can with gauge type hose as above and give it a try..