Fill Flash Help

I want to purchase the Canon 580 EX II and a Better Beamer for my 40D / 500mmf4 / 300mm f4 bird setups. However, I'm a bit concerned about the slow shutter sync of only 1/250 sec, especially with the 500mm. Can I use a faster shutter speed with this flash unit? I've never used a flash, so I'm DOA. I would appreciate any help, or thread info dealing with fill flash and telephoto lenses. Thank You...tom

You don't have to worry about it. All you have to do is set the flash for High Speed Synch, you will do so in the little button on top, not the Mode one but the other one that will also let you choose second curtain flash.
On your manual, look for High Speed Synch.