I think I already know the answer to this but I figured I would be safe then sorry. If I download Sia's wallet and transfer my Siacoins to it on my computer and my computer at some point crash's can I rebuild another computer download Sia's wallet again and enter my seeds and retrieve my Sia wallet from the network?
what trading exchanges will support the fork?
Yes if you back up your wallet/seeds you can boot up a new wallet on any device and import your data.
I believe the fork mentioned is not from the Sia team but a different project so this wouldnt be the thread to ask what exchanges would support the new coin.