Hello Praney,
As far as price, the D5000 is about $800-1,000 more. And as far as a camera system, it's a better camera to build your lenses,etc around too! Also look at the Canon EOS 500D. It seems to me that it is a better camera than the D3000 and as good as and maybe better than the D5000. Here's a great source for information:
http://www.dpreview.com/reviews/
You can see thousands of cameras reviewed, check pricing and make sure you visit the forums too,
Rich Franco
www.richfrancophotography.com