PD stands for Pump Deuse or something like that, it's just what the engines are called (like Ford Zetec). As for oil I went for the VW long life stuff as I can get it for £7 a litre which considering it doesn't need changing for 20000 miles works out not too bad.
I always thought that if you use normal oil it was fine along as you changed it every 6000 miles/6 months approx but not too sure now as I've read that it should be PD specific oil. I'm pretty sure you can get normal PD oil quite easily, best ask you local motor factors or if you are very nice PM Dazboi he runs a main dealer and is always really helpful
Jay