Good luck Tommi there was a micra on pistonheads for £2500 fully prepared, seemed a very good price, may still be for sale. Be careful with lightening the car junior regulations dont allow much lightening.
You could remove sound deadening as said and paint the whole lot red. You can buy stuff called abs carbon sheet, cheap, and looks good, would be ideal to make foot plates and put skateboard tape, as karlj said on top of that.
Not sure if springs would increase the ride height would certainly stiffen it up, what i have seen done is a spring insert put inside the exisitng spring never done it myself but would stiffen it up abit.