Compact Flash cards with my Nikon D300?

I'm renting a D300 tomorrow for a wedding. I normally shoot with a D40x, which uses SD cards. So since the D300 uses compact flash cards, I'm not used to knowing how many pictures each GB will hold? I'm not using the camera the entire time, only during the ceremony. Then for the party, switching to my D40x. If I'm shooting in RAW, estimate how many pictures I could get with a 8gb please?

With my 4gb sd card for my D40 (6.1mp), I get about… 500-600 pictures with RAW
Considering that the D300 is 12mp, and the card you specified is 8gb, I would expect about the same, around 500-600 pictures. I suggest you go ahead and get two CF cards, three even, depending on how much you expect to shoot.