I'd look for a 325 instead.
Intake and exhaust will probably only give you an extra 5 hp if that. These cars are well designed from the factory. Only mod besides F/I that will give you a noticeable power increase would be headers.
None of the non M e46s have an LSD. Most people swap in the entire rear subframe from the M3 since you can't just swap the diff. The other option is to purchase one from Quaife or Wavetrac but they're expensive.