Question for 6 bit coding on 90mm Elmarit

Hi,

I just bought a second hand immaculate 90mm Elmarit which doesn't have the 6 bit coding...

Excuse my ignorance but what changes when the camera knows what lens you have on the front and if I keep the setting on auto what will the effect be?

If I was to send my lens off to Leica in England does anyone know how long it takes or how much to get the 6 bit coding?

thanks

Howard