Hi there,
i am new to posting and forums and a bit new to digital photography too. Learned the basics of photography a few years back, on my dads 40 years old but still alive Roliflex twin lens film camera. Now I'm looking to buy my first Digital SLR. I am an architect and enjoy biking, traveling and art. id like to click landscapes, architecture, portraits, people, a bit of wildlife etc. but not sports.

After researching a bit i have narrowed down the search to Canon 40D or 400D , both with Sigma 18-200 OS zoom lens. i didn't consider Nikon cause Canon has some sort of dust removal system, which i feel is essential being in India. i want a single zoom lens to be on my camera to avoid dust on sensor and to travel light, so i narrowed down to Sigma 18-200 OS. i am confused and have some questions. Id really appreciate if someone can help me in choosing.
1. Plastic body of 400D is good enough for my needs and for my requirement?
2. I wear spectacles so will buying 40D with Live View function going to help much in avoiding the view finder? i don't now how much trouble is it to use the viewfinder with spectacles.
3. Partial weather sealing of 40D vs. no weather sealing of 400D , considering Indian conditions?
4. No top LCD panel in 400D matter much?
5. No spot metering in 400D matter much?
6. Will 40D help me a great deal in taking better pictures? i can afford both 40D and 400D but don't want to spend extra if 400D will suit my needs. Maybe itl be better to upgrade after say 3-4 years to say 60D.

please help