Also does anyone know how AMT charges for overhauls? About how much to overhaul an AMT 180? Do we have to pay VAT tax?
If it is an original AMT180, then it is not an AMT Netherlands turbine, but one manufactured and sold by AMT USA. The importance of this being that AMT Netherlands may or may not be able to assist you with the engine as the two companies were not owned and operated by the same guys and only shared the AMT name for a short time.
From similar experience with two of my own AMT Mercury's (made in the US before the advent of AMT USA), Bennie at AMT Netherlands has been very helpful, but not always comfortable with some of the work I required. The AMT 180 and the AMT Mercury HP are not the same and components are not completely compatible.
If Bennie can help you, he will. You will normally not have to pay the VAT in the Netherlands, but you may have some charges on your side when it comes back into your country.