Hello and welcome to Android Forums!
You are taking a risk when you buy unbranded import devices. Some say the FlyPad3 is the same as the
Gome Flytouch II, but i have seen to many have issues trying to treat it as an exact model match. You're ability to take it to HoneyComb (3.x) or Ice Cream Sandwich (4.x) will most likely rest entirely on the shoulders of the mod community. I would seriously doubt the manufacturer (assuming you can identify them) would put out an update to a new version.
What the sales person may be referring to is the compatibility of the device with Flash Player. If it doesn't have the proper processor or resolution, you may not be able to get the player from the market, thus limiting some content on the pad. Again, there may be a workaround, which you may want to ask about in
General Tablet Talk - Android Forums.
As far as the flash memory, if it's got an external MicroSD card slot, you can go up to 32GB, should be plenty. Be advised that it only adds storage for data and not apps.