Be safe and put the car in gear, or park, hand brake up, use wheel chocks, etc.
Download the service manual here
2009 370z Service Manual Complete ready to Download! and study the front and rear suspension components.
You will need 4 jack stands, floor jack, breaker bar, torque wrench that goes up to 120lbs of torque, open wrenches 17mm, 19mm, 21mm, deep socket set 10mm, 12mm, 14mm, normal 14mm, 17mm, 19mm, extensions. Some of these sockets don't have to be deep sockets but you can buy at sears 6pt deep socket set for $50.
Before you begin you may want to remove your interior plastic parts from your hatch especially if you're installing coilovers and the rear adjustment knob extends too far. The bc br coilovers do not and I didn't remove the rear interior plastic parts. I did remove the front top strut brace to make it easier to access the nuts attached to the shocks.
Roll down the drivers window, unlatch hood, place wheel chocks behind and in front of rear wheel. Take out the scissor jack from the trunk. Then raise the car and place the front on jack stands then rears. Next remove wheels.
Loosen the top 3 nuts that hold the shocks, shown in the fifth pic. Do not remove these nuts until you complete the steps listed below.
Spray penetrating oil on the nut that's on the left side and right side in the first picture, which is circled in red. Use a wrench to hold the bolt in the second picture, this bolt most likely won't move until the nut on the opposite side is completely free. But keep an eye on it and make sure it doesn't move as you loosen the nut. If the breaker bar doesn't create enough leverage, remove the handle from your floor jack and slide it over the breaker bar. I only needed to extend the length of my 2 foot breaker bar by 6 inches. Once that nut is off remove the three bolts circled in green. You will need to turn the steering wheel to get better access to it. Turn your cars accessory mode on and turn the steering wheel. Next remove the nut holding the cable to the shocks, in the third pic. Also, unsnap all cables that are attached to the shocks. Next remove the nut in the fourth pic that is attached to the front sway bar. Once this nut is off you can slide out the bolt that is holding the bottom of the front shocks. But before you do this place the scissor jack to support the bottom of the front suspension to release tension on the bolt.
With the jack still supporting the bottom of the suspension remove the 3 top nuts that holds the shocks. When removing the shocks be careful not to snag any cables.
Loosen the bolt in pic six. Loosen the nut in pic seven and place the scissor jack underneath aluminum arm. Remove the two nuts in pic 8 then remove the bolts that you have loosened. The bolts in the seventh pic should come out easily but if it's really stuck loosen the nut but don't completely remove the nut off the bolt that is attached toward the middle of the car in pic 7 next to the red arrow. You will need to use the scissor jack to line up the holes when you remove and replace the bolts.