waste gate diaphragm

[Nick Lawrence]

1990 200tqa
Suddenly I got way more boost than I should have.  Right away I suspected
the waste gate diaphragm and confirmed with a vacuum tester at home.  I
went to my vast collection of used parts and began collecting up a
replacement waste gate diaphragm. I removed the cap and couldn't get the
nut holding the diaphragm in the center to loosen.  I removed the whole
waste gate to expose the head of the "exhaust valve".  It has an internal
hex.  Is that much dis-assembly needed to replace the part?  Any other
words of wisdom?
TIA
Nick  central Ohio