You may not need an Up arrow, but I do.
This was my Mom's MBP and she upgraded to an Air and gave me this one - super nice laptop. OSX is great for all the typical stuff, but I also needed my laptop to host a program that talks to my car computer through a special USB interface. The app and the drivers for that are Windows only.
No problem, right? Boot camp to the rescue! I created a windows partition and got to the point where I needed to select the formatting option for the partition - the Boot Camp install guide is very clear - you need to format the new partition. I pressed the up arrow - nada.
It actually took me three days and three different Windows discs before I figured out that my up arrow was, in fact, not functioning. I popped the key off and was able, with a lot of squinting, to see that the underlying connection was broken.
I ordered this part - I used ifixit to get in and replace the HDD not too long ago, and the guide was great. The part came in, and I went to work.
It was all very straightforward. Tiny, intricate, and fiddly, but straightforward. The only issue I had was installing the new keyboard into the upper case - it took a dozen tries to get all of the bottom tabs lines up, the side tabs in the correct position, and the backlight power fed through the case in the right position.
It took quite a while, but I was on call this week and took a support call right in the middle of it. My time from first screw to last was close to three hours, but I think it could be done safely in about 60-90 minutes.
You definitely want to take your time, be organized, and to have the right tools for the job. I did not have a spudger; I used a safety pin, with a magnifier and lots of patience. You need a tiny tiny phillips and a Torx (5 I think), a spudger, a means of keeping lots of tiny screws organized, and a good light. And the guide. The guide really helps. A lot.