Simple question, does a 7200rpm HDD use more power than that of a 5400RPM? Next question would there be a notable performance increase of upgrading to a 7200rpm?

The situation is that I have a laptop with a small hard drive, I would like to increase the total memory capacity. Upon a little research about this laptop, I DISCOVERED that it only has a 5400rpm hard drive. I definitely want to increase the memory capacity but if I can also get a speed boost that would be great. However I don't want to sacrifice battery life and extra MONEY for a hard drive that's not going to outperform its predecessor.Yes to both questions.
A 7200rpm hard drive is noticeably faster than a 5400rpm drive.  If it's an IDE drive, it may be a little EXPENSIVE to upgrade, but I highly recommend the Travelstar drives, I have one in my laptop and it's one of the fastest 2.5" IDE drives around I think.  SATA drives are much cheaper.
The battery life won't take a huge hit, I BELIEVE it's in the order of around 10-20 minutes depending on the exact drives and how you use it.It's a SATA laptop.Should be well worth it then.
I can't recommend any SATA laptop drives as I've never used one, but I hear the WD Blacks are great performance if you're willing to pay the premium.
Other than that, just about any quality 7200rpm drive will outperform a 5400rpm model, hands down.