Likely that you wont keep them on there after they've been watched though, given the size of the storage I never do that, just put some stuff on to watch, then when I've gone through it all I just delete it and get more. I use Flexplayer rather than AV Player. Works in the same way an not had any issues with it as well.
Hi Sam, there are some basic infoes you should clear: What video&audis formats iPad support
To get contents such as videos, Pictures, Apps usually use iTunes library to transfer to iPad, of course you also could use some other programs to do this.
Just as said above, you could use the AV player to play many videos, and of course you could use handbrake to convert videos/DVD movies for iPad.