streaming video is not a simple point and click operation, this is for sure. Even if you take great pains to make sure everything's hooked up properly, a great number of user's systems will drop the ball for you - and you can do nothing to prevent it.
1) how to prepare files:
you say you're using dv - capture that to your machine in it's raw native format, AVI for Win, MOV for Mac, these files will be massive massive files. Then use some type of editing software (Adobe Premiereis what I use) to edit the video as desired, then export it to whatever format you decide to use.
I normally have been using WinMedia codecs, 8 and 9 versions to output the WMV format (WMA for audio) and have been really happy with them until I started using Firebird. If you have a 99% Win/IE audience it'll most likely be fine. Go to the msdn and look for material on WMX or ASX files, they're pointers(hints) that help stream the WMV/WMA files.
MOV, MPG, DivX are all fine stuff in their own ways. I love DivX's quality/compression but it doesn't stream.
2) How to uoload the file
3) Is Quicktime enabling required for other file types?
No, see #1 and the MSDN for streaming WMVs, some mpeg types will sorta stream naturally, AVI and DivX are download-then-watch but you can upload em, link em, download and watch, no worries.