Swapping internal HDs

I am getting a 2011 i7 2.5GH MBP 17" (used of course) to gain a bit of speed on my existing 2009 core2duo 2.8GH MBP 17".

The one I am getting only has a 500GB drive/10.7.5, whereas my older one has a 1TB drive/10.8.5, which I myself installed (wow, so easy!). I also have an external 1TB drive which I use as a SuperDuper bootable back up.

Can I just swap the internal drives over? If its more complicated perhaps one of you amazing experts would be kind enough to list a procedure?

I will be selling the older machine on afterwards.