Megatronics 2.0 and marlin need help with the firmware!

Hello Ive recently rebuilt my prusa into a new large printer of my own design using corexy and 2040 and 404020 t slot. ive got it running and printing but there are a few features in marlin.
first i want to connect my reprap discount smart lcd, i have a connector that has the 12 pins but im not sure which wires to put in it.

second i need to enable a thermistor in addition to the thermocouple.

third i need to be able to control 3 fans at the same time independantly.

any help would be greatly appreciated.

wow so i guess no one knows anything about marlin at all.