In body image stabilizing system is a good system whereby it would stabilize your shots even when you have a shaky hand (condition applied). Basically many camera system had this type of stabilizing option, some of them are build into the body, others implement it in some of their lenses. One of the good things about in body stabilizing system was that you can utilize any lenses (correct mount though) and still get the benefit of a stabilized system.
For interchangeable lens cameras system that do not have the inbody stabilizing system, you would either have to rely on the following for image stabilization,
1) Correct holding techniques/ breathing techniques
2) Image stabilized lenses (very very expensive)
3) monopod or tripod
1) and 3) is also applicable to camera with inbody stabilization system, but it will enhance the experience more.
As to NEX-5N do not have too many lenses, well... with an adapter, you can use all the A-mount lenses of native Sony DSLT and DSLR cameras.
And you are right about big size sensor producing cleaner photos (note: Cleaner photo, meaning it had less noise in high ISO)... better picture... not necessary. As I have mentioned before, cleaner, sharper and more contrasty image only make up some part of the overall feel of the picture. The bigger part is the composition... and that is what make your photo interesting.
Thank you very much rhino, you are very helpful. You hv been a great help for me. Thanks for the paitence in explaining stuffs to me