I just did this in my armada. I bought header and cat sets from bear river converters.
First off I am writing this on my phone. Sorry for any typos, auto corrects, and poor formatting. If you read something that makes no sense then I probably didn't mean it that way
The install process took a looong time, like 20 hours across two days.
Here are my notes.
1.If your replacement headers support heat shields, reuse them if you can. Some say it isn't that important, but there are some cables and wires down there and car companies put them there for a reason... I'm paranoid like that.
2. In addition to the 1/2 driver, get yourself a breaker bar. You will thanks yourself later.
3. O2 socket for removal. I have two different ones and neither of them could fit around base of the wire... I bought new ones up front so I cut the wires. The stubby I used didn't fit either. Where did you get your O2 sensor socket that fits around the wiring? My two are craftsman and autozone.
4. Heat shields: if you have any intention of reusing them, be patient. These take massaging to work out. I took them both down the bottom down along the cats. They will want to get caught on many things (like the motor mounts - see my notes on those - and cats). So don't be afraid to bend the units to make them work. Also get your self a rubber mallet so you can pound the out on the old headers so they will fit if you put them back in. This can be done. It just takes time. I worked at this for almost an hour before getting things just right so they could come out. Also, it is important to have the engine jacked up to help you remove these.
5. Motor mounts: I removed them for the drivers side removal and the installation in both sides, and boy it was a lot easier. As long as your engine is supported and jacked up they pop out fairly easily as single units. It also makes it easier to insert the headers and the shields.
Pop them up at the outside while you are underneath (think the square holes on top). That makes room for them to slide down along the block. ( I did one side at a time). Also if you motor isn't centered while on the jack one side will be difficult to remove so a centered engine is key. They go right back in... At least they did for me.
7. Manifold stud by AC lines (this is a bit fuzzy in my memory): I initially broke it lose with a breaker bar and deep well socket.. Then used 3/8" socket with deepwell 14mm. Then a few turns later I switched to a 1/2" socket with u-joint to finish off. If you turn too far you won't be able to remove your socket and will have to back it back in.
This will be a bit of a bugger to reverse, but should be doable with mostly the 1/2" and u-joint.
8. O2 socket for install: a no-go for me again. The NTK sensors I used were too thick at the base of the wire. I threaded the sensor with my hands with the headers installed and shields sitting loosely in position.
Then worked the shield slightly so I could squeeze a stubby wrench in to tighten the rest of the way.
Is there any way to get a torque reading on these? I couldn't... So I guessed.
9. Dip stick tube: be careful with this. I was, and somehow I still bent it very slightly. I have no idea how but the holding bracket ended up being 1mm off and I spent 30 minutes fighting with it to get it's bolt back in.
Regarding sound. The Bear rivers I used sound a bit more throaty under 2000 rpm and are a bit quieter at speed.
Also if your cats were clogged your truck will run much smoother. I was surprised how much better mine ran. I am talking at least 70k miles newer good.