At some point, you're gonna save $1 to spend $2 and it will take you two to three times longer to complete the project as opposed to if you just forked out the dough in the first place. There is no better example of this than with the 5r110 transmission and trying to Do It Yourself. Yes I tried it. And yes I got VERY close to having it done myself. I decided to take it to Andy to have him help me reassemble everything, because for me, it was more about having a tranny that I could be reasonably assured would function and drive right rather than saying I did it myself and then possibly have to go back in replace/redo something.
Like injectors, the number of 5r builders has increased over the past couple of years and prices have really come down. In fact, they've come down so low now that it is IMPOSSIBLE to build a 5r yourself (to the level that you would get if you just bought one from one of the reputable tranny builders) for less than what you would pay a reputable tranny builder. There are not only special tools, there are also little tricks that have to be implemented as well. I guess if you don't care about replacing all the bushings on a 100k+ mile tranny, ensuring that the clearances of the DD clutch pack are exact AND that you get ALL the extra clutches in, OR function testing everything before final assembly then yes you can build it for less.
Furthermore on the injectors, you can not buy nozzles straight from a MFG without being a dealer. So if you're looking to become an injector builder/dealer then go for it. Otherwise you'll have to buy them from an injector builder. And lastly on the injectors, you HAVE to have them flow tested. If for nothing else, just to ensure they all function and flow consistently the same rate. Sticking non-flow tested injectors that you just built yourself into your truck is just asking for issues IMO.
I gotta say man, believe me in that I am ALL FOR THE DIYer. I do just about everything myself. But at some point it just becomes more cost effective to just pay to get it done right the first time and call it a day. From two different stents now of having my truck down for 6+ months at a time, I can tell you that I would MUCH rather drive my truck than look at it sit in the drive way while I F'k around F'k around with little piddly stuff. JMO here. Anyways, you know I'll always answer your questions that you ask me in PMs, but I hope this insight helps you and others who read it. Best of luck with which ever way you decide to go.