Dead easy. You will need a decent spanner that fits the flats on the pedals. The right pedal is undone anticlockwise and the left pedal is a left hand thread and is undone in a clockwise direction. Most pedals will have L or R on the axle for left and right side. A smear of grease on the threads and simply screw them in and tighten firmly. I haven't seen them but I think some pedals are removed with an allen key, I expect someone will be along with more detail if so.