Hi,
Here is a link to the service manual for your laptop.
http://downloads.dell.com/manuals/all-products/esuprt_laptop/esuprt_inspiron_laptop/inspiron-500m_service%20manual_en-us.pdf
It details the necessary pre-requisites and the procedure how to remove the display (click on Display Assembly in contents section), so as to gain access to the hinges.
The hinges are available online. Here are a couple of examples. It is not a recommendation to use either of the sellers. It is just shown to give an idea of what is on offer and the cost. Just search for Dell Inspiron 500m hinge to get results that may suit you better.
http://www.techeeze.com/estore/products/Set-of-2-(two)-Dell-Inspiron-500M%7B47%7D600M-Series-Hinges-and-LCD-Frame.html
http://www.ebay.com/itm/New-Genuine-Dell-Inspiron-500M-600M-LCD-Top-Cover-w-Hinges-0N409-/120525685670
Hopefully this is of some help.