I am no means an expert on car mechanics, but I have been told that YES, the SRT is a DIY job. I believe you have to perform some soldering work on the ECU. I Besides that it is pretty much a remove and replace type deal.
I had bought a Weapon-R intake and put it on in about 45mins. or so, when I realized that the company had sent me the wrong intake. The O2 sensor wouldn't fit. After doing a little reserch I am indeed going with the SRT/ECU combo. From what I have been told, an intake is pretty much worthless w/o a racing ECU.
As for an exhaust, it is also a DIY with the proper rescources. I have been told that the existing bolts are extremly difficult to remove and unless you have access to a garage w/ a lift, I would suggest just taking it to an auto shop that deals with mufflers, exhaust ect. I should only take them an hour or so to do the work and should run you under
$80 bucks. In fact, as I am typing this response, my GReddy EVO2 catback is getting put on right now for $55.
I am going to order the SRT next month from lextsy.com next month. They seem to have the best price @ $525.
Also, I got a reccomendation from the Nopi guys about headers yesterday. Scince I cant seem to find any online for my GS3, I am going to go with custom built ones from this place in Florida. After I deal w/ them an get a price I will post the results.
Once again, I am no expert, but I am learning a lot as I go. Especially with just researching and asking questions on this forum.
Good luck and I hope this helped.
MonStarr