Should I replace the gasket when dropping pan? Looks like I'll need a torque wrench also. My plan is to drain and clean pan replace and refill and then do a coolant line flush. The total should be 8.5 quarts but I think I'll need more as I have to refill before starting the coolant line flush. Does this procedure sound right? I guess 12 should do. I have an 03 Sienna 94,000 miles, last change unknown.