LEBANON VIRGINIA WILL BE LOSING ABOUT 100 JOBS. OFFICIALS AT THE IAC PLANT WILL BE HANDING OUT PINK SLIPS LATER THIS MONTH. THIS MARKS THE SECOND ROUND OF LAYOFFS AT IAC IN ABOUT A YEAR. THE PLANT MANUFACTURES AUTO PARTS AND IS A MAIN SUPPLIER FOR GM. OFFICIALS SAY IF AUTO SALES CONTINUE TO PLUMMET, ANOTHER ROUND OF LAYOFFS WOULD NOT BE OUT OF THE QUESTION.