Hi Jean
You dont mention whether your dash etc is back working again ? I presume it was in fixing this problem that you came across this chip ?
There are many people driving TD5's at high mileage that are happy with the extra performance.However, the extra performance does not come without some penalty , despite what the tuners say. The biggest problem is possible excess heat which the cooling system cannot get rid of, amongst other things leading to high Exhaust Gas Temperatures (EGT) which can blow gaskets , warp heads and destroy turbos unless the driver is careful. Careful means having an EGT gauge fitted so you can back off if the EGT goes too high , or at least knowing when to back off. If you cant meet one or both of these conditions , stay away from the chip.
Otherwise simply "plug in and play " If it feels better and if you can avoid abusing the power - go for it.
Dave