Changing site to local environment

Hi guys!

I'm after a bit of advice and possibly some support here! I'm a newish WP Developer (natural progression from simply managing existing sites then designing new WP sites at work), and I'm also a travel blogger, soon to get on a one-way flight around the world!

I already have an existing site which is hosted through the hosting comp we use at work, but as I've started to edit my sites using FTP and xCode, I'm starting to feel more comfortable editing CSS etc.

I'm just wondering, how easy would it be to change my site to a local environment on my Mac (or ext. HD) and what I would have to do to do this. I'm weighing up the options of whether this will be easier for when I'm traveling around with limited WIFI and can do work offline.

Thanks for any help in advance!

Mark