there are a lot of things that could be wrong with the original turbo engine.. not just the actual engine itrself wiring etc is also an issue.. (esp if its in a cab! )
as for the 1.9 engine.. i wouldnt turbo that.. the bore walls are super thin on them and turboing it is asking for troubble.. also just using a de-comp plate is a crap way of doing it (says me who used to run one! )
if i was you i would find out what exactly was wrong with the original turbo engine and fix that.. or just buy a new one that you know works!