So I tried to follow cleverchimp's instructions for replacing the tube on my bakfiets. He estimated half an hour.
I spent three and half hours, and had a new noise when I was done...I think the wheel must be crooked or off-center, and is rubbing against the "skirt guard" now.
Rather than re-living all the painful details of my three and a half hour flat-tire change, here's my revised version of cleverchimp's instructions, based on my own experience:
0. fashion a stand to keep the bike upright while working on it (unlike the photo). I eventually did this by parking the bike on a kind of wooden box about 10 inches high. The front wheel, the kickstand lock and the bike resting on the box where my contact points that kept the bike stable enough. If you choose to work on the bike on it's side instead, realize this increases the chance of the chain falling off the front chain ring inside the part of the enclosed case that you could otherwise leave alone. Before I started working on the bike upright, the front part of the chain came off three times.
1. Shift the bike into gear "8". This seems to add some helpful length to the cable shifter.
2. Loosen lug nuts (15mm) A normal socket might not fit over this, so
prepared with a wrench or vice-grips (what I used).
3. Loosen tug/alignment nuts (10mm) enough to disengage from the dropouts. ( I completely removed them, but maybe that was over kill.
4. Disconnect brake torque arm (2 10mms) and brake cable
5. Remove rear hatch of chaincase (pry with flat screwdriver) It came off and went back one easily in my case.
6. Disconnect shifter cable. DO NOT remove the pinch nut from the cable itself. If you insert a 2mm allen key in the little hole radial to the hub, and use the wrench as a lever to turn the mechanism counter-clockwise, you can de-tension the cable so the pinch nut will come out easily still attached to the cable (needle-nose helps) You may also be able to use finger pressure to rotate this part around to de-tension the cable.
7. Slide the wheel forward and out. Do your business. Consider upgrading to Schwalbe Marathon Plus, with excessive puncture protection
8. Put it all back together. You'll wish you had a third hand. Tighten the axle in place before tighening the brake torque arm. If you do the brake first, the axle may not be sitting in the right place.
9. Figure out whatever I missed that makes the wheel end up in proper alignment.
The sad irony in my case is that the whole process was unnecessary. When I closely inspected the tube, the problem wasn't that the second attempt a patch had failed. The problem was that there was a second hole all along which needed to be patched.
In my idealism, I did not take the opportunity to install a brand-new tube which I had with me, but put the old tube back into the bike, now with two patches on it.