how can i replace the condensiator on my 2000 altima?

Everytime I turn on the heater on my Nissan Altima 2000 my windshield gets foged and realeses an antifreeze smell. I took it to a mechanic and was told it had to do with the condensiator, it looks like a radiator but only smaller and is located under the dashboard. I need help on how to find it and replace it............THANKS