I've just got myself a nice D70 with the 18-70mm Nikkor lense.
I'd like to get a decent tele zoom lens too, but looking at the range of lenses availble I'm more than a bit baffled...
I see people saying that lenses with wide zoom ranges are a compromise and best avoided, like the Tamron 28-300mmF/3.5-6.3 XR Di lense, true?
Also I'm confused about which lenses do what in the Nikon range (never mind the 3rd party brands)
Am I right in thinking that all AF-S, AF-I lenses do not have aparture dials as this is controled via the camera, and that AF works with these in all modes?
And for AF-G lenses, does the AF work with these in all modes?
Also the AF and AF-D lenses,
AFAIK these do have the aparture dial, so the camera won't be 100% operation with respect to that? And I see from one web page that the AF-D uses the focus motor in the camera body, so I'm doubting that AF will work on the D70 with these lenses?
Link
I've also read that AF doesn't really work below f5.6 due to too little light, true?
I'm basically after something like 70~300 (or 70~200 ish), F4 or thereabouts (can't afford F2.4 yet!) with the same optical quality as the 18~70mm lense the camera came with.
Second hand or new, what do people wot know a lot more than me know?

Help!!
PS As I'm new to decent SLR photography, I sort of expect to buy a cheap(ish) tele lense and then in a few years flog it and buy a decent one once I know whats what and what I like doing.