Be wary of what type of tape you are using to stick the screen back down to the machine. I find OWC tape to be pretty bad in my opinion. IFixIt is better.
Make sure to unplug and replug the microphone cable to the logic board - it's small and very easy to miss.
Also make sure to remove the power button cable from the speaker before you completely take it out.
If you are upgrading to strictly an SSD - (if it's a flash SSD), make sure you remove the SATA cable, else you will experience fan ramp.
And make sure the machine isn't plugged in when you're taking it apart. It hurts, a lot.