You're definitely going to need much more than a 256 MB SD card! When you buy your camera, be sure to get at least a 512 MB, but a 1 GB is preferable.
About those lenses that are being offered with the D50: are they Nikon lenses or are they some other brand? While some lens manufacturers are pretty good with producing lenses with a Nikon mount, others are downright cheap and you would not be happy with their lenses. Check out those lenses...this might not be such a good deal after all. You'd really be best off with the Nikon D50 and the genuine "kit" lens which comes with it. Some people actually don't buy that lens, though, they opt for the "kit" lens that comes with the D70/D70s. Tamron and Tokina make fairly decent lenses and ditto for Sigma. However, in all three cases, there are some really good lenses in their lines and some not-so-good. They are significantly less expensive than a genuine Nikon lens, though, and often almost as good.
OTB