[Thanks for the detailed report Peter...=-)]
"I've pretty much completed the upgrade. Here are the tools I needed:
1) A drill. My old corded has managed to escape the closet it was in, and since I couldn't find it in a tidy manhattan 1-BR, and worse, neither could my wife, a new cordless was ordered as part of our prep to move in August. And for this.
2) A metric set of drill bits.
3) A set of metric hex wrenches
4) A ratchet set, metric
5) A flat-head or phillips-head screwdriver (to take off the reflector)
6) A metric tap set
7) Some grease
8) Thread-lock (loc-tight(tm) or some such. The blue stuff)
10) Recommended: A couple of small black wire-tie in case you need to re-tie the cable ties on the frame that support the o-ring through which the brake, derailer, and fold cables run. Also, some patience. And An extra pair of helping hands if you don't have a bike stand, as I don't. Last, if you do this, order a replacement bike friday stem decal because the double-sided tape that holds that on the bike doesn't come off easily.
The instructions that come with the upgrade kit that BF sent me were excellent, however the first 3 page are not complete, the addendum notes the proper cable routing including the o-ring and the wire ties, and it notes the need to drill into and thread a hole in the new stem. Also, note that the tap needed is an m6x1, which means a 6mm diameter tap with a 1mm spacing between threads. The common sizes in sets appear to be m6x1.0 and m6x0.75, so I was really worried. I hope that BF will update their documentation to note this.
Right now my bike is all in one piece, folded up again. The new stem is more solid. There is some flex, more than I remember... but before that was because the hinge wasn't solid enough, and the give there was noticeable enough that the flex in the stem just didn't mean anything.
The drilling of the front was a bit scary, but since I had the old stem to practice on I built up some confidence and after creating two well-threaded test holes I felt pretty confident.
Of course, before doing this I spent a total of about an hour on the phone with two techs at BF to confirm what I needed to do. Hugh, Tim, and one other rep whose name I have written down at work, but not here, were patient in answering my question and accepting my feedback (eg why didn't they pre-drill the hole and leave the tapping to the user, since that would eliminate problems like positioning the hinge at an angle that essentially screws up the fold, something that the instructions didn't explain clearly enough). The tapping was quite easy.
I noted in my first post that the stem didn't feel as stable as I thought it should. One of the reps very patiently explained how to re-fit the stem into the front forks and how to manipulate the spreader and the bearings assemblies to work it better, and sure enough when I followed his advice later Tuesday night, it all came together.
One note is that the bolts that secure the cable inside the stem is not made to be removed. Unfortunately, it took me a few tries to get my cable routed correctly, to get the distance correct, etc. so I stripped a bolt. Working in Manhattan, there aren't a lot of good mechanic-oriented shops near my office, so BF sent me out a replacement for this along with the replacement front decal, and all I paid for was the overnight shipping.
Overall, I think that David, the BF salesman, was correct in saying that this requires someone with a mechanical aptitude. Certainly if you've done it once, it would be much easier to do it a second time. However, the instructions could use clarifications in some parts, and the addendum they sent me needs to be part of the instructions, because they don't make nearly as much sense out of context, and not at the end (maybe they were meant to be the first thing).