Strut brace is easy to remove, you may have some issues getting to all the plugs leaving it on. Dont read to much into a job, mountain and mole hill come to mind.
Strut Bar Removal for 350Z owners:
Remove the strut bar. Loosen the (two) 24mm jam nuts on the left hand side. Mark the center hex adjuster and loosen it one full turn. Remove the (6)14mm head bolts and (2)14mm head nuts. Use a screw driver on the lock of the slide on wire connector and slide off. Use needle nose pliers to squeeze the snap in wire connectors and push them out. Carefully lift bar out of the way and set aside.
Plug removal:- Here is what you need to do. These instructions are "high-level", but they should suffice.
1. You will need 10mm shallow and deep socket, ratchet, maybe a couple socket extensions, and a general set of pliars as needed.
2. On the drivers side, remove the intake piping and needed.
3. Look down at the driver's side of the engine. You should see the black valve cover just under the outside of the plenum. That is your target.
4. Running over the valve cover is a massive wire harness held in place by a couple of mounting brackets. Locate these brackets in front and back and remove the screws holding them. The wire harness should have more play in it now and you can work around it easier.
5. On top the the valve cover are three black plastic lumps held in place by one 10mm brass-colored screw. Connected to each "lump" is a wiring harness. Remove the harness from each lump. Remove the screw from each lump.
6. Starting in the front, grab the first lump and pull straight out. You might need to move around the large wiring harness while doing this. Once you get the lump moving, you will notice it has a long shaft underneith it. Just make sure not to damage the lump/coil-pack when removing it. Proceed to the remaining two coil-packs/lumps.
7. You should now be able to see down through the head and to the spark plugs. Use the appropriate spark-plug socket to remove them (14mm I think). The socket must have a rubber grommet inside to hold the plug as you pull it out.
8. The passenger side is essentially the same.
9. Reverse the process to install the new plugs. Just DONT DAMAGE the coil-packs. Also, keep everything clean. Fill the spark plug holes with clean towels if the plug is out. The last thing you want to do is drop a screw down that hole. You would seriously regret it.
Hope this helps. It is really pretty simple and should only take a couple hours if you are taking your time. As for gap, I think the stock gap is 0.041-0.044", but I am not certain.
Can we ask your skill level in mechanics?
What is your location, someone maybe close who could offer help.