2.5TDI gearbox and engine light ?

well i have had this car for 2 years why oooo why did i buy a tiptronic its going back in for its 2nd gearbox thats 2 in 35 thousand miles and to cap it all the engine management light has come on again (1st time it was a new box costing god know what)
what i need to ask is how many sensors has the car got running off of the management system and how long is the warrenty on the gear box and ECU both were fitted just over a year ago (20.000 miles) and how much should it all cost of not covered ?