Car is just bought by a kid just learning to drive (he's 16).
2004 Mitsubishi Lancer ES

Neighbors asked me to teach him how to replace the oxygen sensor (due to
emissions code).

The threads were stripped and "filled" with some kind of hardened "metal
paste".

The new part is a Denso 234-4739 (marked 485000-4060, 07U05)
The old part is a Denso (marked 234000, 8643, 07E23)

What would you suggest?
- Tap the threads? (22mm hex nut)
- New exhaust manifold?

http://www.bild.me/bild.php?file=3234632o2sensor01.jpg
http://www.bild.me/bild.php?file=8064061o2sensor02.jpg
http://www.bild.me/bild.php?file=6399144o2sensor03.jpg
http://www.bild.me/bild.php?file=1574232o2sensor04.jpg
http://www.bild.me/bild.php?file=9418974o2sensor05.jpg
http://www.bild.me/bild.php?file=4183674o2sensor06.jpg
http://www.bild.me/bild.php?file=5856176o2sensor07.jpg
http://www.bild.me/bild.php?file=3486734o2sensor08.jpg
http://www.bild.me/bild.php?file=9694112o2sensor09.jpg
http://www.bild.me/bild.php?file=5019152o2sensor10.jpg