LastZion said:yeah it is possible... but I can't see why you would want to. Upgrading to get more space is one thing, but simply to go from 5400 to 7200 doesn't seem worth it to me... but thats just my 2 cents.
The cost will be more expensieve than it would be if you had of just done it when you ordered it right away.
Regardless... here you go: http://www.pbfixit.com