Lower it, Best thing you can do to improve the look. I can't give a recomendation because i beieve the shock towers are different then the RWD cars. Look into some Bilstiens or Konis and some decent springs.
For the Short shifter you have some options but you can do it cheaper by swaping your lever with some other bmw parts, I have a z3 1.9 shift lever and I like it, you can also do a couple other z3/z4 levers but you will have to bend the selector rod. Let me know if you want more info and I will try to find the link to the different ones available.
By chin spoiler i assume you mean the lip, just get an iS lip (like mine) and it will look great, I have always liked the little iS spoiler on the trunk or some of the Mtech ones are cool too and a little larger but still no wing. The Mtech 2 spoiler/wing is by far the sexiest though.