5 - 30 minutes
So, I had a friend over, and we were doing some drinking, and I had my Macbook (Mid 2012 Unibody) plugged up to the tv. Apparently after I went to sleep my friend started feeling sick. He ended up vomiting and I suppose he couldn't make it to the bathroom, because he ended up throwing up in the empty pizza box beside my Macbook... well... mostly... I woke up the next morning to a puddle of puke about the side of a pancake on my open computer, right on the keyboard, and by the looks of it, it'd been there for a few hours. I immediately shut it off and pulled the battery, but the damage was done. I cleaned it off and let it dry for a few days before turning it back on (amazingly, it still ran). Several keys were inactive or triggering other commands, my trackpad was being janky, my hard drive was making weird noises, my battery life had decreased by about half, and my optical drive was completely broken. I'm a working DJ, and learning music production and sound design, so obviously this was a very big issue for me.
I ordered all the parts (at least I thought I did) and got them in the mail a few days later. I downloaded iFixit's mobile app for iphone (SUPER HANDY!) and got to work. I had to disassemble the entire machine in order to replace the upper case, and then as I was putting it back together I was able to just swap out old parts with replacements. I opted to get a hard drive caddy and swap out my optical drive with a second hard drive (now rocking 2tb of storage, it makes me very happy) since I have the external superdrive for the Macbook Air. With iFixit's guides on the app, it was a breeze from start to finish and I got it all done in a matter of hours. I consider myself a handy person, but I know nothing about computer repair, so for me to be able to flawlessly repair it to fully functioning status was a pretty great feeling. Couldn't have done it without the step by step guide with greatly detailed pictures. I discovered a couple days later that my airport/bluetooth card was also damaged by the incident, which is not a huge deal, just an inconvenience and I plan on replacing it when I get my next paycheck.
If you're replacing your upper case on the Unibody model A1278 (not sure about other models) the guide doesn't mention it, but you need to pull the battery level indicator off of your old upper case and transfer it to the new one. Another thing I didn't know that fortunately didn't bite me in the hind quarters, was the risk of static shock. I didn't know this was a thing, but a simple static shock discharged from your body to your computer's sensitive inner parts can practically destroy your computer, so before going into your computer's innards, make sure to look up online how to ground yourself so that you don't risk killing your beloved computer. Lastly, if you decide that you also want to replace your optical drive with a second hard drive and intend to use apple's external superdrive, be aware that the drive was only intended for use with Apple computers that do not originally have an optical drive, so it's not a "plug and play" accessory. You have to go online and find directions for rewriting one of the scripts so that it will allow the drive to be used, just be careful because an incorrect sudo script can seriously mess up your computer.
OH! And for the love of all things holy and unholy alike, MAKE SURE YOU KEEP ALL THE SCREWS SEPARATE AND WITH THEIR RESPECTIVE COMPONENT! I cannot stress this enough. You will save yourself a major headache. I used sandwich bags and labeled them with a sharpie.
1 TB 5400 RPM 2.5" Hard Drive
Tri-point Y1 Screwdriver
MacBook Pro 13" Unibody (Mid 2009-Mid 2012) Trackpad
MacBook Pro 13" Unibody (Early 2011-Mid 2012) Upper Case
MacBook Pro 13" Unibody (Mid 2012) Hard Drive Cable