Tough call mate. Providing your engine has been looked after there's no reason why you can't turbo it and get a heap more power. The most important thing is getting it tuned correctly; lots of them are not done right and they end up destroying the engine.
The 1HZ has about 50kW at the rear wheels. A good turbo will take that to about 100 kW. Gturbo come highly recommended.
However, it all comes down to the work that needs to be done on your vehicle in the future, and the value of any modifications you have fitted. Expect to have other repairs required, as they are getting on in age.
I have spent way more than I'd like on our 80 series, which is running the 1HDT engine (the 12 valve factory turbo).
Another option is to install a 1HDFT engine in good condition; you will get a lot more power, better economy and they are just as reliable. Not cheap either way.
Ultimately only you can make the call; think about what its going to cost you over the next x years, versus trading it in. 80's are very capable cars, and there isn't a whole lot in diesel, sub 20k that compares. If you are one keen on doing the harder 4WD tracks this is important. If not, then it doesn't matter so much
Good luck
Aaron