1 - 4 horas
I had my wife's Macbook with us on vacation. We travelled in a van through Australia. One time I accidentally stepped on the Macbook which was underneath a pile of clothes. The only thing that was broken was the LCD screen. A serious area contained dead black pixels.
I ordered recently a new LCD screen since my wife wanted to use her Macbook again - we had an iPad by then.
I didn't know there were so many and such tiny screws in a laptop!
What I learned from replacing a part in my iPhone 4 was you really have to read the instructions, don't jump from image to image as you will destroy something.
The disassembly took me over an hour, being very careful not to break anything.
Reassembling the LCD was easier, but when the entire laptop was built again, I noticed a part that was not installed correctly. Not having the patience to go back to step 61 (yes, really, one of the first steps of putting it back together) I gently convinced the part to snap into place. No further damage.
iFixit's guide's are golden. I feared in the dismantling process that one key item might not be the same as in the guide. But it wasn't. They really know their stuff.
Tape every set of screws on a piece of paper or something. Also I find it very useful to use a white desk as you will notice any little parts that escaped.