I have the .sql script for a MS SQL database, and I'd like to try using Filemaker instead. Is there any way to use the SQL script for the empty database to recreate it in Filemaker, or do I have to rebuild it from scratch?

Take a look at the 2empowerFM SQL Runner plugin.  You can plug in standard SQL Create Table scripts and have them work (mostly) as you would like.  There are some differences between what MS SQL uses and what FileMaker expects.  Basically, if you could use it in ODBC, you can use it in FileMaker.  It's *far* better than having to do it all from scratch.