to humour you, as you obviously can't be arsed to look:
if you have a 1.8, easiest thing to do is to fit the uprated head gasket and remote thermostat kit, keep a close eye on the coolant level, perhaps fit the remote coolant level warning kit. all of this is detailed on this fine forum should you require further details.
it may be possible to fit a different engine, there are numerous threads, in particular, the member known as Mad Hat Man recommends a rover 220 engine, but how hard this is I wouldn't like to comment.
The 2.0 diesel is a reliable if uninspiring engine, the td4 is a much better option. However, the work involved in converting from a 1.8 to either a 2.0 diesel or td 4 is immense, and would involve changing the engine, gearbox, fuel tank, fuel lines, ecu's, wiring looms, as well as having to run in fuel return lines etc.
of course the true answer to your question "which is a good engine to fit to a freelander" is one that never goes wrong, pulls like a train and does 400 miles to the gallon. but that don't exist.
good luck.