You are correct that Adagio OLEDB will let you get information out of Adagio AP, however it is read only and so you will need another method of pushing information back.
Adagio AP does have "import" capability from a number of different file formats, including text, CSV and Excel.
We also have a programmer's API that allows you to write directly to the database but you must manage all referential integrity issues. Depending on what you want to add/modify/update this may or may not be a a big deal.
The "import" is the safer approach as it protects the integrity of the database. In any case you are on the right track.
Feel free to Email me directly with more information on what you want to write to the database and I will let you know which approach I would recommend.