I think it's pretty safe to assume you have the sport package, but if you want to be 100% certain, there are a number of VIN decoders available online which will tell you what options your car came equipped with from the factory. You just need the last 7 digits of your VIN.
As far as offset vs. centered bushings go, I noticed a massive difference because I went from totally shot non-M rubber bushings to totally solid mount delrin racing bushings with offset geometry. It's hard to really compare the two worlds, since I'm sure I would've noticed a big difference even if I had just replaced my worn out non-M bushings with the same thing. Honestly, for regular street driving I don't think you will notice much (if any) difference in how the car feels from a handling standpoint due to the offset bushing geometry alone. That said, since the offset M3 bushings are nearly solid rubber (unlike the non-M bushings, which have big voids in them to soak up vibrations from road surface irregularities), you will probably notice a difference simply due to the increased stiffness of the bushing material itself.
I upgraded to bushings with M3 offset geometry for a number of reasons, and one of them was that I knew I was going to eventually upgrade the rest of my suspension to full M3 geometry, including the stronger M3 upper strut mounts. If you don't plan on doing that down the road, I probably wouldn't bother with getting offset bushings, and would recommend just getting the centered M3 bushings from the '96-99 M3s instead. That way you will have correct wheel placement, and will still get a handling improvement due to having slightly stiffer control arm bushings compared to the non-M bushings.
Make sense?