Re: LENSE QUESTION
Well one good thing good about Nikon is every lens ever made for Nikon will fit the new body's as well as the older body's.
Now a 2.8 telephoto lens is going cost you big bucks for a 300mm 400mm less its a older one, and might not have Auto focus (AF) some of the older one do have AF but not on the lens your body must be able to AF the lens some of the cheaper Nikon body's don't have it, but I think the D50 does.
Even a older 300mm 2.8 lens is going cost you about 2k maybe a little more maybe a little less. You can get the 80-200mm 2.8 lens pretty cheap from like $400-$900 its all in what model you get. If your looking to get a 80-200 2.8 I would be willing to sell you mine for about $400 bucks I just don't use it anymore and I just boght a 300mm f4 lens so I want to sell it to cover the cost of that lens. If you think that is something you would like to have you can PM me and I can tell you more about it and show you pictures.
If you need any more help I would be glad to help.