Laptops may have a lot of benefits, but upgradability isn't always one of them. Even if you'd never think twice about cracking the case on a desktop to pop in more memory or another video card, you might pass on doing anything with a laptop—their cramped interiors and the specialized hardware you need just to get inside are instant turn-offs. And if the laptop in question is an Apple MacBook Pro, you might dismiss the idea as soon as it comes to you. After all, Apple doesn't have an upgrade-friendly reptutation.
Don't let that stand in your way. You can give your MacBook Pro more and faster storage. Doing so will require some minor surgery and void your warranty, but you'll probably find the process easy enough to be worth the risks. (And not having to pay an Apple tech to do it for you is a definite up side.)