I finally found some time to wrap the headers. My head was spinning after reading so many conflicting points of view about the benefits and drawbacks of wrapping and then about the different methods of installing it, but ultimately I needed to get it done because I want to replace my melted turn signal and I don't want it happening again.
I tried to follow Mol's guide (
http://www.talkmorgan.com/ubbthreads.php/topics/370813/1), but the removal of the headers was a nightmare. The bolts that connect the headers to the engine have minimal side clearance (none of my sockets could fit without hitting the header) and the bottom bolts are impossible to hit without a very long drive extension. The bent washer adds further difficulty.
I ended up soaking the wrap in hot water and installing it with the headers still attached. It was my first time doing anything like this, but I like the way it came out. I just hope it stays intact and doesn't cause any damage to the headers over time!

