I'm building a room in my garage. The cement is cracked towards the back corner; about 15 sq ft. This section of the floor is about 1/8" lower than the rest . I'm wanting to patch it and hopefully level it out, but I'm afraid there may still be some issues when I lay down the laminate. Is it safe to go with a laminate that has underlayment attached, or should I spend a little more and get a thicker separate underlayment?