The official service interval is lifetime oil. But most ppl change the oil and filter at aprox 100.000km
Mine was changed when I got my car with 167.000km on the clock. Basically because I didn't know if was ever changed and because the car was remaped when I got it.
The engine code IS M57D2. The first generation diesel engines from BMW was M57 and was 184hp in the 330d. Later on it evolved to 204hp and 231hp as ours are.
The gearbox is a 6 speed ZF box capable of transffering aprox 600nm according to ZF. But I know of several 330d's tuned to aprox 300hp/700nm. Mine will quite soon be one of them :-)
'06 E91 330dA Sparkling Graphite|19" AvantGarde M359 Satin Black|335i brakes|Bilstein B16 IRC|Powerflex|GroundControl|Wagner|Ecotune|Turbo Dynamics|Zimmermann