My .2 for what its worth.
If you upgrade your throttle body to a 85mm or especially the 90mm. It will require a tune to rich up the fuel, so you don't lean it out too much. I went from the stock 80mm to the 90mm throttle body and threw 2 lean codes shortly after due to getting more air then it was calibrated for based of the fuel/air ratio.
But throttle bodies are very easy to install, literally 10-15 mins tops. Like you said, its just the 4 bolts and the sensor.
The 180 Tstat is just as easy, just make sure you dont break the bolt off in the housing
, which is not common, I just had the misfortune to that costly mistake. I would also recommend going with the Jet Tstat, because it was a perfect fit on mine and if I recall when, helping with Bryan's (non Jet) Tstat, we had to grind it down to make it fit properly. So spend the extra 5 bucks.
There is a thread somewhere on Tstat fan settings, I know there is one on the LX forums. This is very easy to do with the programmer.
Catch cans debate, I was very skeptical at first but I got one installed and it has been catching so much bypass oil, its crazy. A mod that is well worth getting. Very easy to install as well.
Here is a pic of my catch can with the Z bracket below to give you an idea of the install set up.
Regarding exhaust mods & CAI. Cant go wrong with any exhaust setup, it boils down to personal preference. I would just recommend finding a lightly used one, if you can to save some coin. In regard to CAI, I like the Stackperformance and LMI True Cold AIr Intake that sits down below the engine bay. As you see in pic above, I have the short ram CAI, that sits behind the headlight for now. Mopar in the last couple years just released a fender sitting Air Intake. Stack and LMI are the composite plastic that probably stays a little cooler then my aluminum one but again, personal preference.
Now as far as the cam, many things to consider, such as recommend supporting mods, which can quickly run your budget up. Example depending on which cam, you may have to get a higher stall converter ($500-$900), Timing chain kit ($150-$275) is highly recommended, Tune ($300-$500) will be required for sure.
ATI Super Damper is suggested ($400). Depending on how big the lift and aggressive your cam is, you may have to upgrade your heads, and that is a costly mod. Is there anything else that I am missing? Personally I dont think I would go with the stock 6.1 or 6.4 cam, I would do an aftermarket cam, there are many options, heck you could even have a custom grind cam based of your supporting mods. So you can see how a $500 cam could cost quite abit more in supporting mods, and the labor isnt cheap either, unless you do it yourself.
There was this Red Challenger R/T that made some very impressive numbers on the dyno, I am talking a few ponies more and quite abit more torque then a stock SRT8. Richard (BYUchallenger) had Long Tube Headers, UnderPulley, HiFlow Cats, CatBack Exhaust, Intake and Tune, Phil, Ben and myself were very surprised to say the least, when Richard put down more torque then all of our SRT8s and we all have different model SRT8s of course they were all stock with canned tunes, CAI and Exhaust.
While you are saving up, do plenty of research on what works best for the new 5.7 R/Ts. Im not sure if yours has the MDS or what. Check the Challenger Talk forums and LX forums, as someone just went through exactly what you are planning.
Good Luck and keep us posted! Also PM, Brian (ChallengeIT), I know he just had an aggressive cam installed in his R/T Challenger with many other supporting mods such as CNC ported Manifold and Head work I believe.