I remember my mechanic telling me that my front pads were wearing thin and suggested I change them the last time I was at the shop for an oil change. The brakes were working fine and the yellow light never came on before, so I held it off. That was a pretty long time ago. So, now the lights have come on, but it doesn't stay on. It just came on while at a stop with my foot on the brake and disappeared when released. Anyhow, I need to know what is a reasonable estimate for new brake pads on a 1990 190E. I think it's only the front that needs to be changed, but I'm not sure. Should all four be changed? Thanks.