My late 2007 MacBook pro came with a 160GB hard drive, which was nearly full (understandably) after 4.5 years of use. After checking around some message boards about DIY upgrades, I found this guide on iFixit:
As recommended, I purchased the spudger, T6 Torx Screwdriver, and Phillips #00 Screwdriver. These tools were invaluable (especially the screwdrivers) and were easy to use. I couldn't imagine needing the fancier screwdrivers for this process.
The step-by-step guide was spot on. Absolutely no ambiguity or mistakes. I had never opened a MacBook Pro before, and my upgrade was complete in less than an hour.
Even though the guide mentioned to be very careful when removing the keyboard/trackpad because it is connected to the logic board by a ribbon cable, I still managed to yank it by accident, disconnecting it by force instead of delicately with the spudger. Some revisions to that section of the guide might explain exactly where that cable is and how to do this properly, with a few more specifics.
The best piece of advice I had received which I want to pass on is that you should use scotch tape to attach all of the screws to a printout of your guide (attaching them to the relevant step when you removed them). There are too many screws that are the same or similar to keep them all straight otherwise.