Problem with the models is that their are "transparent" in physical sence, a player will not collide with them and you will have to use Radiant (and the only program for Q3 afaik) to create brushes which will reform your models to some extent. It is also a very inefficient in the fps aspect as well as gameplay. (otherwise called : model spam).
Radiant is a nice tool to map with. Not very powerful, but will allow you to get the basic geometry done, after which you can get the models to fill the harder parts.