This weekend I plan on replacing the glow plugs and reaming the holes.
Rather than renting a reamer, and after finding out that Diesel911 was out of stock, I wound up buying a reamer through Baum Tools' eBay store (alkyracer101) for about $40 including shipping.
The tool is nice, however I was a little disappointed that the hex end, the end you put the wrench on to turn it, is made out of aluminum stock. I also think the hex is 1/2" and not 13mm, as all of of my 13mm wrenches are rather loose on it. I hope this does not lead to stripping the hex while turning it. I also wonder about the threads of the tool cross threading easily. If there are serious issues, I may just cut the hex part off the tool and weld the reamer portion to an old glow plug.
These are observations so that someone who is considering buying one in the future knows what they will receive.
I will give an update after I use the tool to let everyone know how it works.