Hey mate. There is heaps of info on here about chips. There is actually a stickie thread in this area. Just do a search. Many Peolpe have chipped with no problems. Some have chipped with problems. Good luck.
If you are worried about your engine get an egt and boost guage. These will provide you with real time data as to how your engine is performing. if your egt's get too high or boost is spiking then you can save your engine before any permanent damage is done
There's plenty of us out there running chips, and who have experienced no issues whatsoever. As the old story goes, you only ever hear about the ones who have problems.
Fuel usage depends on how you drive it not the chip - it is a product of volumetric efficiency. The more volumetrically efficient an engine, the less fuel it will use on any given task.