I'm a total Nikon fan for a number of reasons such as quality, platform stability and reliability. I used to work in a camera store, and have been doing black and white photography on and off for about fifteen years.
A DSLR is the right platform for what you want, not simply because it's a DSLR, but because of the ability to adapt to what you need. You can add one (or more!) flashes to light the subject correctly, and you can change the lens to suit the subject.
As noted above, the lens is the singular MOST important part of the camera. A lens for a DSLR is inherently much larger than a point and shoot, and will therefore let in a lot more light, allowing for faster shutter speeds and better quality images. Those tiny lenses on pocket cameras are absurd - in that it's like comparing a dog to a racehorse. There's a lot of selection for lenses, Nikon's "ED" glass is their better quality. Canon typically doesn't use "glass", but instead uses Crystal Fluoride (or used to), which tends to be lighter, but has a greater expansion/contraction rate in extreme temperature ranges. This is why you see Canons at sports events, and Nikons for outdoor. I think making the decision based on weight is silly, have you seen the tripods they use in football games?
Remember the "jack of all trades, master of none"? That applies here, too. A 28-200 lens sounds convenient, and may be acceptable for general use, but you'll get less distortion and better quality with a set of lenses, such as 18-35, 28-70 (or 28-105, which I don't think is made anymore), 70-200, and fixed focal lengths beyond that. There's other options too, like fisheye, macro and portrait lenses. You'll probably find that you stick with one lens most of the time. I don't do much that needs telephoto, so I have a 28-105, and a macro lens, and am perfectly happy 98% of the time. Based on what you described in the OP, the standard pairing of 28-70 and 70-200 would be better for you.
I keep using film focal lengths because I always forget the digital ranges, but a DSLR has an inherent 1.4 or 1.5 multiplier unless you buy a REALLY expensive one. So, the digitals come with an 18-55, which is about the same as the 28-70. It also means you get "free" zoom (good for you!) and have to work/pay more for wide angle (bad for me).
TL;DR version: Buy a Nikon D5000 kit with two lenses at B&H/Adorama/Newegg/Best Buy. D3000 kit may be ok, but the 5000 is a bit more feature rich on the camera side. You don't need a D300, despite how shiny it is. (And trust me, it's VERY shiny.)
edit: Oh yeah, find somewhere to take classes on Photography with regards to composition, aperture/shutter balancing and technique, regardless of camera purchase.
