valve cover oil leak

I have been informed that I have a small oil leak on the driver's side valve cover. The dealer wants to replace both sides. What are the consequences of only chaging one side or not doing it at all. It is a 01 S Type 4.0.

Thanks

Oil will foul your coils and sparkplugs. With a leak this might be happening
already on your driver side. If you do it yourself your talking $4.00 a plug
and $50.00 each coil. If dealer does it for you add about $150.00 to it.