Multiple typos and spelling errors in exercise 6

[schwentker]

1. Typo in introduction:
   stock purchas agreement

Should be:
stock purchase agreement

2. Typo in introduction:
   due dilligence document

Should be:
due diligence document

3. Filename typo in output:
   The file being referenced has inconsistent spelling:
   "Legal Due Dilligence Documents.docx"

Should be:
"Legal Due Diligence Documents.docx"

This spelling inconsistency appears multiple times throughout the notebook and in the generated Python files, which could cause file lookup failures if the actual filename uses the correct spelling.