I use my Macbook as a DVR for OTA television. I was going to buy a new Mac mini to replace it, but installing a bigger hard drive and more RAM saved money and extended the useful life of the Macbook.
Extremely easy to do the replacements. The online guides were very helpful.
Delete unused files and applications on your existing haddrive before using SuperDuper to make the new harddrive a bootable drive. You need to buy the USB drive case to hook up the harddrive to do the copying (it's part of the package that comes with a set of tools too).