I need a new hard drive

[World Traveler]

My computer is a Dell Inspiron 8600 purchased in December 2003. It has a 32 GB hardrive and only about 33% free space now left on it. I like my laptop and am only interested in getting a new, larger hardrive for it.
Is this possible? I would like to go to something like a 100 GB hard drive. Do they make them that large and with the ability to still fit in a laptop? I also want to transfer all the data and opp erating systems on my current hardrive to the new one.
So, the end result would be that I have the same computer, just more storage space.
Any tips, leads, or advice.
Plan B is to just get an external hard drive and transfer everything to it except what is absolutely necessary to run the lap top. But I don't like the idea of an external hard drive. It just seems to me like they would be too easy to damage.