I bought a 15" Macbook Pro that came with 4GB of RAM, and I wanted to put 8GB into it. I bought the toolkit because with as tiny as the screws were, I felt like it was a good idea to get the proper screwdrivers rather than risk stripping the heads. Also, I wanted the ever useful spudgers. I will probably upgrade the hard drive at some point too, so this toolkit will come in handy at that point and every time I want to modify this machine.
I followed the instructions on iFixit. It was very simple and straightforward.
I have changed memory many times in all sorts of machines, so there were no enlightening moments. I will recommend being careful with the battery plug since the pins are thin and you will probably touch the mainboard in the process. Also, I could've used screwdrivers I have around the house, but having the right tools meant I didn't risk stripping the screw heads. Macbook Pros are nice and expensive machines, so it is a good idea to have the right tools