aftermarket headunit for 323ci...2000 model

Hey guys,

Im considering to buy a 323ci. The only setback is that ive got a 1500 pioneer headunit sitting at home that i wanna install if i do consider buying this car. If i install this, i heard the steering wheel buttons will cease to work, and also it will trigger the security component, so if in the future i wish to sell the car the old headunit wont work and the steer wheel buttons will go to waste...can anyone confirm this?

Thanks ppl!