what kind of oil

you can run most any brand you like.a5 w 30 probley 5 qrts plus filter

If it doesn't have too many miles on it I would run synthetic.  I run it in all my newer vehicles and have not been disappointed.  True, your oil will run you about $35 (plus tax), but your peice of mind is priceless.  Others will say that it doesn't matter, but nowadays its more important than ever to take care of your automobile (investment).

It will probably take between 5 and 5.5 quarts of oil.  Check after you're done with the oil change and make sure you're at proper levels.

full synthetic 5w30, since it's a 2003 it started with synthetic from the factory.  I use mobil 1, it may cost more but
it evens out because of the mile difference ie 3000 vs. 6000

I agree with synthetic, but make sure you have an oil stabilizer during the summer time... it'll run really thin and pending on how thin, it might knock on the first couple revs... during the winter... straight synthetic