Well with yours the "alternate type" would be a bodykit for a JR or JS series one Vectra (common known as a Vectra B Pre-Facelift or Vectra B MkI (yours is a 'Facelift' or 'MKII'). I'm pretty sure they'd fit yours - the bumpers would be fine because you'd be taking the ones you have on off, and I think with the side skirts that are on there at the moment you just take them off to get back to what the prefacelift has).
A remap is where you alter the way the ECU "drives the engine."
Auzvectra comes round to your house (I'm guessing) and installs it. It'd be $600 I think.
As far as exhaust noise goes, you can tune the pipes by adding things like resonators to get the sound you want. I'd suggest consulting an exhaust shop for this.
Interesting to hear that it's a belt because I thought they went to chains with the c22sel engine; maybe I'm thinking of the z22se. What do you have Shay?