63whoopie,
On a single piece drive shaft there are no alignment issues so marking isn't needed. I sure wouldn't put heat on the shaft, and the method you outlined would be pointless anyway.
R&R of the u-joints isn't complicated, but it is specific, and if you know how to do it, you can get it done. The explanation isn't short, so I'll let some body else chime in with that. Good luck.
Stuart
