Regarding severing legal rights - I met with a fertility specialist in our area who said that if we had a known donor, we could set up a sort of "directed" or "designated" donor for us. The donor could donate to the doctor's office, do paperwork and STD testing with them, and the we would basically "buy" the sperm of our designated donor from the doctor - like a really small-scale sperm bank, but cheaper than a real sperm bank. We did not end up going this route for other reasons, but I did learn that there are some doctors out there who will put themselves in the middle as a mediator. I believe Pokey is right about STD testing and quarantine. It is more expensive and complicated, but the legal grounds are more clear.
Fresh sperm (including shipped sperm - I mean, any sperm where there is not an intermediary) has less of those hoops to go through, but doesn't come with medical assistance (if you decide you need or want it) and has more gray legal ground. Basically, you have to be comfortable with the risks and confident in your donor contract + the intention of the donor you're working with. The FDA regulates what doctors can do with fresh sperm, so the medical help you can get would be limited if available at all.
I have heard of people finding KDs so many different ways - asking around the community, friends-of-friends, craigslist, etc. The KDR is just one place. My acupuncturist offered to help me find someone! Think of it as a weird kind of really awkward blind dating and put out a lot of feelers until you find the right person. Good luck!