It goes straight in but you need the gearbox as well to make it easy, LR did a conversion kit of all the bits, engine, gearbox, radiator and intercooler when the tdi first came out. My daughter has one (didirangerover on here)which was converted, has been excellent with really good fuel consumption around 30 - 35 even better on veg oil as well !!
Only weldy bit is putting the engine mounts on the chassis but not that difficult. best bet is to get a rusty Disco and transplant the lot