Andy,
It is true with all the medications that a recipient takes to keep their body from rejecting the kidney makes it quite impossible to harvest that kidney and use it in someone else. As far as I know, I don't think transplant recipients can even donate blood because of all the antibodies and drugs. Some transplant recipients decide to donate their body to science upon death to be used for research.
The other question you had about how you go about organ donation after death is a good one. Everyone should have a living will and advanced directives. In this way, if something should happen to you and you are unable to make health care decisions for yourself you appoint a proxy who will make decisions for you. Checking organ donor on your license is a first step to becoming an organ donor upon brain death. In addition, make sure you have this conversation with your family so that they know what your wishes are in the event of brain death. you can contact your transplant center and speak with a social worker about setting this up. Before my surgery, I had prepared a living will and health care proxy (my husband). We spoke about our wishes in the event of brain death. You can also speak to your family physician or lawyer to help set this up. These are legal documents and can be changed at any time.
Hope things keep going in the right direction for you. As you say, time does heal or at least the loss becomes more tolerable.
All the best,
Sherri