I have just been and driven my first ever X5, and its the model I want which is the 4.6iS, its a 2003 model with 70,000m.

As it was my first ever drive and I am no mechanic, can anyone advise on some queries, possible fixes, and any idea of cost ??

1) When I pressed the button to fold the mirrors in, the drivers side one closed but then re-opened and the passenger one never moved. The engine was running at the time, does the car have to be off when you attempt this, or are they broke, and if so what is the fix ?
2) this one had the sunroof option, and when pressing 'close' (with one-touch close) from the wide open position (not tilt) the sunroof closed but then re-opened, it would only close fully when the button was held ? reasons ?
3) The front parking sensors did not beep when up close (rears worked) the salesman said he had switched them off, and the PDC button was lit, was he telling the truth, does the PDC button switch the front sensors off ?
4) What is the RDC button ?
5) I have a 330iSE and am used to the sound of the straight six, I realise this is the V8 and will have a different sound, but I was suprised that under hard acceleration (I had waited for the rev counter lights to go out) the engine sounded rough and quite harsh (it did not 'feel' rough or harsh, there was no vibration). Is this the difference between my six and the V8 or should it still be quiet ?
6) He did say that a previous owner had removed the metal tyre valves and replaced them with rubber hence the tyre pressure alerts would not work. There is an error message on the display about Tyre/Pressure inactivity, or something like that. A) Is this OK to replace with Rubber. B) Can this be put back to how it left the factory and how much would that cost. C) Can this error message ever be removed or will I have to see it every day ?

Thanks for any advice you can offer