Isn't that supposed to be the last of the Agfa 400 stock ? Or maybe they have another manufacturer now.
I also have a Pen EE and i think the highest iso is 200asa, but you could certanly pull the 400 speed - or assume that most of your pics will have a bit of sky so you need to give one stop exposure-compensation (the selenium cells are not very directional and tend to pick up some light from outside the strict frame area.
The EE was my carry-around camera for years and is limited only by having no focus, although the short lens and the fixed-focus works fine most of the time. The focussing feature came in with the next model I think.
To start with, to check the camera out and make sure the selenium-cells are alive and kicking, I'd suggest buying a short colour print film in the local supermarket. Go through that in a few different lighting situations (lots of sky, no sky, strong backlight, try the flash-socket etc etc) then have it developed in one of the 1-hr places. Within a couple of hours total you will know the state of the camera.
Good luck
🙂