Dave,
There are some excellent responses here. Everyone pretty much hit the nail on the head, I just thought I'd throw in my experience: it was really quick for us (about 2 months from first crossmatch to surgery) but we hit a last minute snag and had to have an additional crossmatch done 4 days before surgery (not including the pre-op crossmatch the day before surgery). When the results came back compatible, I got really nervous and thought the same things you are thinking. Having to fill out a living will and medical power of attorney didn't ease those thoughts, either. Then my rational brain took over and reminded me of all the things I learned during the process and that I was in experienced and capable hands. It also helped me to remember that I was at this point in my life for a reason, and if I died during the process of saving someone else's life, at least I would know that I had done something noble and selfless. (sounds kind of morbid, but I had to come to terms with the (very, very remote) possibility of death from complications, and that was what worked for me) Those thoughts quickly faded and I started to get excited about taking part in a (literally) once in a lifetime opportunity. I also found it helpful to focus on the little things like how I would get around after surgery, what I would do while I was home from work, etc... and remember that there are a lot of people like us that have done what you're doing - most of us make it through without a hitch! Focus on the majority of 'cases' not the minority. It's worth reiterating that you would not be accepted as a donor if you weren't in exceptional health.
I'm just over a month out, and I feel great! I took a total of 3 weeks off work with surgery on the first Tuesday. I'm still easily tired and a little tender around my large incision, but no general soreness at all. In fact, it's easy to forget I just had surgery until I lean on something! My recipient's outcome was a little rough going at first, but he is now doing very well. If I could go back and do it all over again, I would do it in a heartbeat.
In hindsight, the nerves paled in comparison to the amazing feeling of helping someone who needed me.
Love,
Rocker
P.S. - I felt soooo wonderful after surgery to know that everything went well for both of us that when I saw my surgeon in the hallway on the way out of recovery up to my room, I high-fived him. I was that happy.