Who did you buy the truck from?
How long have you had the truck?
If a dealer, even if it was sold "as is", still has some obligation to help with the repair, if not all of the cost of parts, less labor. At least that is how it used to be.
If a private party purchase, check your state laws, you may have recourse. In Michigan you do.
The only reason I say this, is because ALL 6 INJECTORS don't ALL fail at once. You are looking at some major $$$$$$, into the thousands! Sounds like someone "KNOWINGLY" dumped their problem on you! Most states have laws on the books for situations like this.
See if you have any recourse, if not, or you don't want to go there, here is my . 02.
Look up Jennatty(sp) Racing in the links section here at TDR. Give them a call, and ask for Chris. They use a place in Maine to rebuild there injectors at a very reasonable price. I bought a set off of them, they work.
Also, have Chris email, fax or mail you their injector removal/replacement instructions. This will give you an idea if you are up to the job. And trust me, it will take longer to do the job then you think, though it really is not that difficult. If it is your first time, plan at least a full day to remove and another day to install when you get them back. The instructions are nicely detailed with some pictures. But, you will need a ft/lb torque wrench, a stubby 3/4" wrench and a crow foot 15/16 or 7/8's, can't remember right now, metric and standard sockets with a couple of feet of extensions and a good breaker bar. Sears has what you need to do the job. Forget the inch pound (in/lb) torque wrench, you don't need it, just snug. The actual work is pretty easy, but you need to be as flexible as a monkey to get to the rear injectors.
Been there, done that, and I am still in pain just thinking about it. Pay a mechanic, and you supply the injectors
Oh, you will also need to order a new grid heater GASKET. It will crumble when you go to remove it. Or, you can use some high heat liquid gasket in its stead, the gold colored stuff will work fine.
Mike