I have not heard of a conversion utility. I would make sure the 525 was running version 7 of the pix code. Using a sonciawall which has a browser based configuration front end I would use the new ASDM utility to configure the Pix. It will show you graphically through some wizards if you wish how the flow of traffic will be through a given interface.
You can even use the wizard to build a vpn tunnel.