trim packages

Hi, I'm new here. I just bought my first ISUZU I found a real nice 03 rodeo. Since I bought one I notice them everywhere. I've seen some that are the LS and I think there is just a S package too. Mine don't say on it anywhere what it is. How can I find out? I'm sure it has allot to do with the options (trim) it has on it. Mine is loaded, power sun roof, seat, anti theft system 6 disc CD changer, pw, pl, I was reading the owners manual and the only thing I see mine missing from the options is fog lamps. You would think if they were going to load it up they would add fog lamps. Anyway, I noticed some have the spare tire on the tail gate/rear hatch & some have it underneath. Why? Mine is underneath. So far I'm real happy with it. but after reading some of the postings here, I'm a little scared. I know I will be checking the oil on a more regular basis after what you all said about the ISUZU oil consumption on the 3.2L. Thanks for any help you could offer.