Aaah, nice kit, nice colourscheme, I loved building it and was utterly PO'ed when it broke during a move (years ago).
For the step between layers, I'd advise using the micro mesh system, going from... is it 3000(?) up to 12000 grain. You can also just maybe get away with using Tamiya's polishing coumpound. Unless you really layed on the yellow and you have a real big step.
It is all gloss underneath, so clearcoating before decalling should not be needed. If you want to, go for it... I tend to decal, then clear. You have a school of thought that says decals are applied over everything on the real car, so that's how it should be to mimick the real thing. I'd rather protect my decals. Just be very carefull if you clear with TS 13, if applied too heavily, it can "melt" paint and decals. Light mist layers...