IIRC that $500 is a base price not including parts, and i think Jim posted that he almost always has to replace parts when doing re-builds. Just something to think about.
How cheap is cheap for the injectors? The turbo and everything else really isn't an upgrade or worth much. But if its a Late 99 they are AD's, which are roughly 140cc. They make a good entry-level injector, and will run decent. I ran em for a while, with and without tunes, and i've talked to some other guys that are running them. If you can get them for $3-400ish, and they are low mileage and the truck ran without issues, i'd get em. You probably want/have tunes already, so just get em re-burnt for the injectors and run it.
BTW you can run em all day long without any tuning and it'll run fine. My truck seemed doggier down low, but pulled a lot harder up top. Tunes helped it a bunch.