A leaking front seal will allow oil to get into the area where the timing belt is located. This will cause oil to get on the belt and can cause damage. Since the timing cover must be removed to access the front seal, it is recommended to replace the belt while you are in there. Also, the water pump is driven off the timing belt. Replacement of the water pump is always recommended when replacing the timing belt for two reasons. First, it is easily replaced at this time and it is good preventive maintenance. Secondly, the water pump bearing is under tension from the timing belt and develops a wear pattern. Replacement of the belt without replacing the pump will cause the new belt to wear the bearing in a different pattern, often causing leaking in a very short time after the replacement. This would then result in having to repeat all the labor again to replace the pump. It is easy to see that for $400.00 labor, you don't want to do that again in only 2-3 months. as far as the VTEC valve is concerned, I don't see a relationship to the oil leak. It could just be something else the mechanic found during the inspection. I can find nothing in the remove/replace procedures that requires replacement of the oil pan gasket. Again, maybe something additional that is needed from visual inspection, but not needed for the front seal.