Computer upgrading question?

I have an MSI A6000 that I bought about a year and a half ago. It still runs well although the hard drive is getting full and I recently came across a few large programs I'd like to be able to run, namely some Autodesk software. I have the boot discs for the computer. So would it be a good idea to buy a new, bigger hard drive and reinstall everything? Will it get my computer back up to new condition? Or should I just leave it alone since it doesn't run poorly to begin with and make room on the hard drive? Thanks for your answers.