Using an existing database

Hi All,

I'm fairly new to Grails/Hibernate - so hopefully this query isn't too noobish.
Currently I'm in the middle of designing a web client to access a database (previously accessed with a desktop client).  The only catch is, there is significant data already in place that is reliant on pre-existing tools - which means it's highly unlikely that I can restructure the database in the near future.

Outside of changing the *DataSource.groovy files to point to the relevant database (and provide user details), is there anything I would need to be wary of in terms of using the existing database? 

For example, is it likely to cause problems that some "standard" fields are not there (like id, version)?

Thanks!