2nz-fe to 1nz-fe engine swap

[tristanp]

so i have an 05 echo with 450km on the clock, engine seems to go ok but uses oil, blows a little smoke after a big downhill, i was offered a write-off platz a year or so ago for $150 with only 100 on the clock , i thought sweet a fresh motor and pats for the echo. on further investigation (after it was home) i realised it was a 1nz. have done a lot of reading on line about the swap and info seems to be pretty inconclusive about having to go for the new ECU or not, since the ECU does the ABS/ airbags etc i think it will be easier to stay with this one , its only an increase in capacity, the O2 sensor will pick up running lean and sort it out? maybe? , only one way to find out....
also the 1nz is an auto, so i will be swaping the flywheel etc and starter off the old motor, i wonder how hard this will be ?