Yes, and there are a number of videos on you tube showing how. Look up your specific model since not all laptops disassemble the same. You can even put an SSD in for ultimate speed if it's within your budget.
The general concensus among laptop users though is to store data on an external hard drive (since it's easier than getting into the laptop) and use the internal hard drive for the operating system and programs. You can load programs from an external hard drive but they will load/refresh slowly (unless you have USB 3.0).