Upgradind USB 2.0 to USB 3.0 possible?

Hi friends,

I own a late 2008 unibody Macbook Pro 15in and iam looking at updaing to new MBP just for the USB 3.0 since my Nikon D800 supports USB 3.0.I shoot tethered and i guess USB 3.0 will be a good choice.One of my friend suggested that i can upgrade my existing system to USB 3.0 using the PC express slot.But is it advisable and effecient as built in USB 3.0 ?.Can something like this be done ?My system is out of warranty and my Nikon Camera Control pro trial version ends in 4 days.Thanks in advance

regards
Prasana
http://www.rprasanaphotography.com