I know a 1.6 Almera conversion has been done in the UK with relative ease.
A SR20DE has been put into a micra.
To my knowledge, new engine supports need to be made, drive shafts from the new engine need to be shortened in length to encorporate the slimmer body.
Also you'll have to look at uprated brakes, and possibly uprated suspension to take care of the extra weight!!!
A 1.6 or 1.4 Almera engine will require a lot of modification to make it work, although not as much as a 2L.
You might as well go for the CG13DE (1.3 L) Micra engine if you're not looking for a major improvement in performance, also it is basically plug and play!!!