Burned Exhaust Valve MC (Questions?)

[shawn]

I am 99% that I've burned an exhaust valve on my '89 200 non-Q 150K.  My
diagnostics are the horrible "missing" sound and the fact that I held a
large Autumn leaf to the exhaust and it was intermittently sucked in rather
than blown out.  I could buy a gauge and check compression, but ....

Questions:

What is the most likely cause of the burned valve to begin with, I've read
it comes from running lean, but how does that happen?

I Googled the archives and came up with some excellent help:

Audi Rebuilt head at Carlsen $480, $300 core.  (Local Machine shop wanted
$640 to rebuild mine)

"The amended checklist for the MC head removal"  Phil Payne original as
modified by Igor Kessel.

To accomplish this job and much needed timing belt change I need to
purchase:

Cylinder Head (above)
Head Gasket
Intake Manifold Gasket
Exhaust Manifold Gasket
Valve Cover Gasket
Turbo Gaskets
Head Bolts
Timing Belt
Tensioner Pulley
Water Pump

Am I missing anything?

Is there anything else I should attend to when I have it torn down this far?