A question about collisions.

After importing go to the object in your project folder, and then go to your import settings in the inspector and turn on generate colliders.

I already did this. The physics involved were very weak and my character, if persistent, can travel through them. Should I code something to stop that or does Unity have something built in?

1 thing you really have to do to get correct physics is set the mass in the rigidbody OR character controller etc. Else you should try put the speed down of the object.

I changed the mass but nothing changed to be honest. Is this because I am using transform.Translate? I hear this ignores physics, is that correct?

Maybe you should try using a different controller to move your character. i personaly like this one very much, and indeed translate does ignore physics.

http://docs.unity3d.com/Documentation/ScriptReference/CharacterController.Move.html