Depends on whether you want to pursue the other company or not.
If not, you at least have two engines to play with. If the head and turbo off the second engine are OK than you could swap them both over, but when you take the head off the first engine make sure you get to the bottom of what caused the water leakage. It could be an overheat followed by gasket failure.
In which case, make sure the deck of the old block is flat and there is no damage to the pistons/cylinders.
Then remove the head on the new engine, check it out thoroughly to ensure it really is viable, then fit it to the old block with new gaskets. If you need help with checking the head out, come back on here!
The plastic dowels aren't meant to hold it in place, they are there just to make sure that the gasket and block goes back on square, it is the bolts that hold it all in place.
Best of luck.
Oh and swapping the turbo should be easyish, but do check there isn't much play on the bearing.
All the very best
Stan