Yes, the complete SMS'es are there. Also the text part of MMS'es is stored there but the pictures in the messages are stored separately (and maybe other attachments too, I have not checked with MMS'es containing sound etc..)

To access just the messages would require understanding the DB structure and writing correct queries to retrieve/manipulate/delete the records. It seems to me that the messages are tagged with consistent id's so this should be possible.

I have to confess it's been really long time since I have looked into insides of a sql database... I did some course work on postgresql in the university but that was last millenium