I have a 1988 YJ. I got a quote of $900.00 for parts and labor ( new pressure plate, clutch disk, slave cylinder, pilot bearing) from one shop. Another shop qouted me a labor only rate of $600.00 if I provided all of the parts.
Preen is a pre-emergent weed prevention product. It prevents weed seeds from germinating instead of killing existing mature weeds. Preen works on a wide variety of annual weeds, but it won't have an effect on perennial weeds because they already have established roots.
Pre-heating is just that; getting the oven hot before you put the food in it. It is necessary for the oven to stay hot while you cook your food. Cooking times are based on a pre-heated oven. If you put food in a cold oven, it will totally throw off the outcome of the recipe.