I have a 20D and I would say you are making a good choice.  
Seriously, the 20D has several advantages over the 350XT---the ones that are important to me are the higher ISO settings and the bigger buffer.  Also, I find the Rebel XT to be too small for comfort in my hands.  Even the 20D with battery grip is a tiny bit small---I liked the feel of my old 10D with grip.  But there are many improvements over the 10D that made it worth it to me to get the 20D.  Just the control layout and startup time are a huge improvement.
As for the lens---that's a hell of a lens you're intending to get and I doubt you'll be disappointed.  You might want to get something at the wider end and the longer end as well, though.  I'd reccommend a Canon 10-22 or Tokina 12-24 for a wide lens, and a Canon 100-400 or 70-200 f2.8 for the long end, if you have the money.

Quoted: Well I listed that lens because I wanted to know if it was good for digital cameras or more suited for film.  I found that the lower the f-stop the better results I have.  Maybe I just need a tripod!

It's great for digital OR film cameras, and trust me when I say you won't ALWAYS have a tripod with you. If the price scares you away from the Canon 24-70L, try the Sigma 24-70 f2.8 Macro.  Hell of a lens and you can buy one for around $400.  Great sharpness and colors.  A good, affordable lens combo would be the Tokina 12-24 f4 (around $500), the aforementioned Sigma and a Canon 70-200 f4L, which you can find used on the buy/sell boards of forums like www.fredmiranda.com for under $500.