Thing about cameras and questions should I buy this or that does not make sense at all. Camera itself has no difference. Somehow people got an idea that they will get at least second most expensive item from some manufacturers model line and here you go- it just going to gather good pictures itself. It is your brain and eyes what makes a difference and knowing your camera.
Yes, camera matters in a sense that you really don't want to get some sammoyoung product, but camera manufacturers tend to be very close in terms on selection. Of course newbies in SLR system does a little bit worse, they lack quality glass and so on, but I see amazing pictures taken with pinhole cameras (and they have no lens at all!) too. Also good SLR body will save you time when you will actually take pictures and not look for some settings in a menu.
Yes good glass make a difference. But you can take good pictures with cheap kit zoom too. What is the difference? If good glass will allow you to take pictures without a tripod in poor light, I think it is good enough reason to get one. And if you can afford one...
Car shows? I think you want to travel light. 18-200 lens is heavy, but way better than two heavy lenses. Night shots? Well you could do with many lenses, just get a tripod. Digital is very forgetting. It is good tool for beginners and pros too. You can erase and not waste any "film".
Do you want to follow whim of your buddy or just get some attention with big camera?
"I know the DSLR body won't last as long but am just trying to step up a little until FX DSLR's become affordable. The D3 is out of my price range, and as a first generation I'm not keen on being on the bleeding edge. A freind just got a Phase One back for his medium format but I'm nowhere near as well heeled."
Also it depends what do you do? Do you earn a living from photography? Do you need to print big posters? Do you shoot RAW? Is it your firs digital SLR? And so on. There are a lot of misconceptions just because of deceptive marketing. A lot of people believe that more megapixels will guarantee them good pictures. Actually a lot of people I meet who are curious about my camera (I have nothing fancy, just rebel xti) ask first question - how many megapixels it has? Phase One for example is a headache. It creates more problems- WHERE THE HELL YOU WILL STORE THESE HUGE FILES? You begin buying camera and end up buying hard drives or what ever your storage system preference.
So don't be fooled by marketing. Images make a difference, not fancy cameras. As for question what makes bigger difference- camera or lens I would go- lens. It will outlast camera (unless you will break it).