These questions are probably better asked in The Modding Dungeon where hopefully someone may be able to answer them. The matter of IP rights would need to be answered by someone more familiar with law than I am; I know in general terms that it's generally a Bad Thing to try to make money off something without express permission to do so, but beyond that rights holders often have very different conditions, e.g. Zenimax at one end, where they won't even allow asset re-use within the same games series to the makers of Stalker who said pretty much "do whatever you want with them".
But for your own perusal,
Norbyte's Export Tool will do everything you need.
