David ,
Thanks for highlighting the cracked oil filler tube. Some of us(Me too!) get so obsessed with the complexities and frailties of this engine that we forget an elusive oil & vacuum leak can be a simple as a cracked oil-filler tube !
Exactly where did it crack ? That would be a great help to others. Any idea what caused the crack ? Now you have examined it, is the tube brittle (from heat?) or is it impact damage ?
The coolant tank destructive dismantling- creative ! But I guess replacement procedure will not be the reverse of the removal process :-).
Excellent work - thanks for sharing.
Related:
http://986forum.com/forums/general-discussions/56299-coolant-tank-hell.html
Another coolant tank replacement DIY