I have an 04' 6.0 PSD just turned over 50K miles and I love it. No problems whatsoever. Preventative maintenance, just do it.
FWIW, I tow a 8 x 20 enclosed with about 8000 lbs in it daily and my Cat 257B several times per week. I drive it like I stole it too.
The LORD is my shepherd, I shall not be in want. He makes me lie down in GREEN PASTURES