Maybe the parts might cost that if you are lucky to find all the things you need. But you'll need so much more than just a turbo and some pipe work.
It will cost you double that. There are several people here and in SA that have done the conversion. If you are not doing it yourself because well you keep talking about a mechanic doing it. That means there are labour charges involved. In the end its going to be a unique machine. But its going to cost you a lot to do it.
If the mechanic doesn't want to do it then you can't force him to take the work on.
Like I said before buy some books on Forced injection and read and learn and then dive in if you have a large enough budget.
You can add turbo's etc to the engine but it will take a hit on reliability. An the TS isn't exactly the strongest engine known to man as it is.
A correctly tuned turbo engine will be no less reliable than an N/a engine. But car's already fitted with turbo's have had a lot of money going into research and design. Your budget is only tiny to do the same thing.
Alfa 166 2.0 Twinnie - LPG and a few trick performance parts