It's done! I joined the two halves last night and am really pleased with the result. I need to do something lovely on each edge, probably a crochet to keep it from rolling. And then I will block it and get photos posted.
It was a very unusual way to do the kitchner join and the actual process was not described well in the pattern directions. I did read everyone's input about the process on the yahoo group connected with the shawl, but still felt it was a process that would either present itself logically to me as I attempted the join, or fail miserably. I was not about to accept failure, because the thought of trying to unjoin something made of those tiny stitches was unacceptable. The alternative was for it to work the first time.
So I took the one piece of advice I had seen the most often, to first purl (wrong side row on each edge of the area to be joined) with a very large, and strongly contrasting yarn. I was knitting the shawl in lace weight yarn and so I choose a bit of worsted weight handspun in white that was conveniently laying around. Cotton was recommended and I can see why, because my choice of wool meant the lace yarn often wanted to stick to the wool yarn when I was removing the contrasting thread. But I didn't have cotton thick enough and all it meant was a bit more caution as I removed the wool.
The first step was to purl each section's wrong side row with that contrasting yarn. Then I slipped each section's stitches from the circular needle I had been using to a long straight needle, one size smaller than the circular to help the actual edges lay flat and not follow the curve of the circular needle. I made sure the two straight needles holding each section would line up right, so right sides of the two sections were on top and the end on the knitting needles were to my left. I started the kitchner stitching from the right of the shawl where the points of the needles were.
The first dozen stitches were very fiddly. For one thing I was trying to work with the shawl laying on the table and stretched out flat. As I completed the set of kitchner I would release the stitch of the contrasting yarn and pull it out. The actual sewing of the kitchner was going through the lace yarn, NOT the contrasting white yarn. So the sewing was happening below the stitch that was on the needle. However, it made it pretty easy to see the lace stitch and to slide my threaded needle through it, either knit or purl wise.
After that first dozen stitches I gave the sewn area a good tug, and that's a good thing because it really did need to be loosened and stretched along the seam. When I did that, the seaming practically disappearred. Kitchner is amazing that way.
Once I got the rhythm going, I realized it would be so much easier if I had the knitting needles up off the table and held in my left hand side by side. Then it was really easy to get a rhythm going and keep track, the front needle always had a knit direction, slip the contrasting stitch off and pull out, front needle purlwise in next stitch, back needle purlwise and slip contrasting stitch off, then knitwise in the next stitch, back to the front needle, etc etc.
It took about three hours to complete the grafting. The stitch markers had been left in place from the original patterning, and that really helped keep the grafting even. The only thing I would have changed was I did a few knit stitches with the contrasting yarn instead of purls, following the original pattern and it was harder to graft those stitches. I would purl everything for that one row, just to have all the stitches going the same direction. Otherwise, I really was impressed with how using the large contrasting yarn helped with the grafting process. I hope my explanation here will help me remember how it was done, and maybe help someone else that attempts it also.