Did you not drive the car before you bought it?
Fitting a SMF in place of the factory DMF usually creates a "rattle" at low rpm.
That is because the SMF does not have any transmission damping properties.
If an HR then box will have to be removed.
When in there replacing the CSC then best to swop out the clutch cover and plate and possibly the DMF.
Expect to pay circa £2000.00 with an uprated CSC
Sorry, I don't do guesswork I am afraid.
You will have to get all the wiring hooked up correctly and then follow the troubleshooting guide in the Nissan workshop manual.
Looks like temper orange to me.
Go to any paint shop and they will confirm the colour using their paint swatch cards and they will also be able to mix the paint up for you.
That is what I fit to all the cars that come into my shop for a rear bracing replacement.
https://www.torqen.uk/nissan/350z/suspension-steering/braces/20746-350z-ultra-racing-rear-lower-brace-4-points-rl4-1259.html
Give them a shout @Coz@TORQEN