Very basic overview!
There's 4 bolts under the carpet that hold the mechanism to the car. To undo these you need to take out the front seats and front seatbelts to get the carpet pealed forward (or you can cut the carpet) then from underneath - bend the heatsheild so you can get at the two bolts that hold on the plastic cover - once this is off you'll see a wheel which you need to take the split pin out of, un hook the cable from the wheel and then the level should lift straight out.
Of course it helps to have the car jacked up enough to get under it, properly chocked and not on the scissor jack! It might help to unclip the cable from the rear trailing arms - there's a plastic clip where the cables passes through the rear sub frame assembly.
Why do you need to change the lever - is yours broke?