I did mine at 50K. Took about 2 hours with ordinary extensions and a ratchet.
The original plugs looked OK except for the front ones from each bank, which were severely eroded.
Recommendations:
- cold engine
- blow out spark plug head hole with air before taking out old plugs
- use a locking extension with a socket with the rubber inside
- think twice about using anti-seize compound on threads
- use small amount of silicone grease inside plug boots
