In OEM right click on a table and select view/edit contents to see the data. However if its more than a few thousand rows you need to start filtering.

Yes a machine could have a database and not be listed in oem. You really need someone to quickly run you through oem (and get you started on the database you want).

Toad is a great tool for developers. A similar thing is called sqltoolz, available on sourceforge.net and http://sqltools.net/.

Not quite as good as toad, but its totally free.

Bazza