Just swap them and enjoy your ride

Only thing to do: like after every tyre change (or after you checked the tyres pressure) you may have to "recallibrate" the new pressure.
If your e53 is a facelift this is done by startiung your engine, pressing the RDC button for about 5 seconds until the RDC dash light turns on and then driving some meters until the RDC lamp in your dash turns off.
I don't know if the procedure differs on the pre facelift (without/with RDKS)... But just take a look at your manual if you are not sure...