As far as the 400D goes, its a great camera, Ive had one for about 5 months, only complaint is the dust reduction hardware & software do next to nothing. And I see this as a big problem because its a buy word Canon used to suck me in:)

I'm not sure about the Tamron gear either. You’re definitely looking at a good starter focal length range. 18-200 would be plenty to get you going. I would suggest going down the local camera shop and trying a few lenses on a 400D body.

Tip: I good entering point into the manual modes is to start out with AV mode, its one of the most effective and easy to use modes on any SLR. You will find that a lot of photographers shoot in this mode, OK if you’re doing action and the like maybe TV. But for the most part you’ll find working in AV mode the easiest and hassle free. Dont go straight for full manual mode, this can lead to serious brain injury:)

Good luck and let us know how you go.

-Michael

I never intended to make art.