Check if the fan port is still safe, and try not to use your laptop otherwise you’ll break it or in your case melt it and it can cause irreversible damage.
Since I have a similar model, I can guide you to replace your fan, I will highlight the main steps for now because I’m not at home.
You already took off the keyboard/mousepad so I will continue from there, now you need to remove these components:
* Battery
* Hard drive / SSD
* Wifi
* Optical drive
* Screen cables
* Any other cable connected with the motherboard (like extra USB ports)
As I remember the motherboard is a little bit tricky and you have to removed softly but since you melted some plastic and I don’t know what else, then you need to be careful with it, could you add a photo after you unplug everything from the Mobo?