Hope you factored in the cost of the bits when you bought the car!
If you want new parts from Honda;
interior door handles are £300 each
seat cushions can be bought separately to to the side cushions. If the black colour has rubbed off the seats, it can be touched up with shoe dye (not shoe polish!).
complete seats are like £1000+ each.
centre thing is a speaker. It doesn't make much noise. It is powered by the amp in the subwoofer. Each speaker has its own amp.
cam belt needs changing at 60k miles, or 7 seven years. Costs around £500. Find a NSX approved dealer. I think Trident, Chiswick would be yours. Can also get water pump changed at same time.
All parts can be bought for less from America.
If your fear of staying alive, outweighs the thrill of making the corner, brake.