ok, so insurance, yes you should declare it whether it be a box or a remap as it is a modification. but honestly, come on!
as for your chocolate tronic boxes, well, you need to find out the safe limit for torque on them. a decent tuner will have this information to hand and will map your car to suit. it may well be that they ramp up the power and add a nice curve of torque with a safe upper limit. its like everything in life, you pays ya money, you takes ya chances!
if you have a manual go for one of those diesel tuning boxes (if you really dont want to take it to be rempapped), if you have an auto take it to a well reviewed tuner.
Tuning doesn't break cars, stupid breaks cars.