wiring advice: Ramps 1.4 with Fan, LED, z_probe switch (no replies)

My hot end will have some LEDs to light the print area and a fan for the Jhead. In Repetier, I see a slider for fan speed.

Can someone explain how with Marlins, I can control a Jhead 40mm fan and 3 little leds?

What pins.

I also have a microswitch to z_min pin for auto bed leveling.

I don't know enough about lectronics. Am I correct I do not need to wire 3 seperate grounds for the LED/Switch/fan, I could have all three wired together and only the positive wires to the RAMPS?

I'm trying to have less wires.

Anythoughts.

Thanks

Alex