Question 1: How do I setup my Picasso96 to run on my Voodoo3 2000 card?
Look for a file called Voodoo4&5guide that came with your mediator software. That will also work for a voodoo3.
I would also suggest you register with Elbox to ensure you have the latest drivers, if you haven't done so already.
Question 2: How do I setup the OS3.9 internet software to use my FastEtherent card and broadband connection?
No idea. I use MiamiDX. I think OS3.9 comes with Genesis or something like that.
Question 3: How do I setup AHI to use my SoundBlaster128 and can it passthrough the Amiga sound somehow?
Once your voodoo card is working, just launch the ahi prefs and adjust to your tastes. Yes, you can pass through sound. I have a cable with RCAs on one side, and the other plugs in to the line-in on the SB128. (Only downside is that if the card doesn't get initialised, you won't hear sound from the paula.)
Question 4: I'm totaly clueless on what is needed before I can see TV through my FlyVideo98 TVtuner
Get the other stuff going first. :-)