A tuner will not cause you to blow head gaskets.
However, what will cause your headgaskets to blow is when the oil cooler gets clogged, causing the coolant to flash boil and rupture the EGR Cooler. When the EGR cooler ruptures, it dumps coolant into the cylinders which increases cylinder, lifting your heads.
The first thing you need to do is get a monitoring solution, like an Edge Insight, scan gauge II, or Dashboss to monitor your Oil and Coolant Temps. They should never be more than about 10* apart. If they are, your oil cooler is getting clogged. You also want ot make sure your FICM volts are never less than 45, 48 is great. Adding a Fuel pressure gauge is important too, as low fuel pressure wil kill injectors, not cheap trust me
Here are some links you should read up on:
Things to Consider about Owning a 6.0
Bulletproofing the 6.0
Personally, I wouldn't tune the truck until you get a monitor on it and find out what condition your engine is in. If everything looks good, and you have taken some of the preventative measures, like upgraded fuel pressure sping and coolant filter, make a call to one of the many reputable tuners and get some custom tunes written for your truck. That will make it really come to life.