I remember reading that the oil prescribed to generally maintain real steel weaponry can actually damage AEGs due to the fact that AEGs are not made of the same materials, nor do they work in the same fashion. Unless one of the veterans here gives you the thumbs up, I wouldn't let anything that's not specifically for the AEG near it.
As for common maintenance, all you need is 100% silicon oil. If you ever want to open up the mechbox and regrease, you'll need a proper grease, though I couldn't tell you what specifically to get. For my mechbox repairs I've needed molybdenum gear grease and silicon O-ring grease. Though I highly doubt that's necessary.
Hope that helps somewhat. I'll try to find some links for you on common AEG maintenance.
Here's a link to common AEG maintenance:
A link on internal maintenance: