I searched for quite awhile before starting the header project, and during the "nightmare"! I'm the original owner of the 02 SCrew. Pretty much an unmolested truck. Believe me, I've had my money's worth at 198k, and hardly a problem! Beside regular maintenance items only real issue was 3 blown out spark plugs around 120k (I did the time-serts myself, and no issues since).
I've had a ticking sound for about 2 yrs and finally decided it was the drivers side exhaust manifold (which the headers cured). 1st things first - Take out the inner fender liners! What I thought would be a days work at best, turned into 3! The biggest problem was the motor mount brackets were shielding a couple of the header nuts/studs. So we had to take the mounts off (replaced them due to the mileage/age of the truck) and relieved the new mounts so they wouldn't interfere with the new header/studs/nuts. 3 of the old studs sheared off at or below the surface of the head, during removal. I bought a "head stud tool kit" for the modular motors, that made removing the broken studs a breeze ! Honestly - A BREEZE ! After all yer jacking with an aluminum head, and u don't want to screw that up ! ! ! NOW, for the controversial ; header selection! I went with some amazon $140 stainless shorties! Not the cheapest, and definitely not the most expensive (but I'm on a serious budget) and almost everything is either made in china or a chinese knock off ! Anyway the fit was pretty good, except for the EGR bung, it was about 15 degrees off ! it took some creative cutting and welding of the connector to get it hooked up. Also some of the header pipes made it difficult to install the nuts on the studs. As far as the performance - I'm happy, over the last 2 months it feels like it changed the mid range the most, but overall, a HP increase. Id think a "tune" would probably help a bit more. Ive had a performance cat back (single) system on for about 15 yrs as well as cold air induction/an Edge tuner for about 10 yrs (but only used the "tow" setting. I've heard their "power" tunes were a bit harsh on the 4.6.
Was it worth all the hassle, yeah. Just a lot more work than I thought it was going to be (but rarely is it ever less work)!