1999 Infinity Q45 Spark Plugs

from Silver Spring MD

I purchased a 1999 Infinity Q45 with 72000 miles from grandma in georgia and took to infinity dealer in bethesda MD to have looked at. Grandma has an extensive history with dealer maintenance so I trusted. I mentioned to service advisor if multi point check could be done and that i was wondering how much spark plugs replacement would cost. He said that it would be too difficult for me to do on my own because plenum had to be removed on the 4.1L V8 and that it would cost 480 dollars. I believed him and know as I look at engine I think I got suckered. My question is does one have to remove plenum to get to plugs? what do guys think