2001 Mercury Sable power steering fluid leak

I am pretty sure I have a leak in the power steering fluid because I seem to have to fill it every couple of weeks. The service manager at Mercury said it is rare for this model, but if I do have a leak, do you have any idea how difficult or costly it is to fix it?

Thank you so much for your help,

Barrie[img:e5731385fa]http://www.2carpros.com/forum/automotive_pictures/162171_Picture_093_1.jpg[/img:e5731385fa]