What is the estimated time to replace spark plugs on a 2001 5.4 exp?

TIME?!? You mean, how many miles before you have to replace it? Whatever it says on the box. If you're talking about replacement time, about 5 mins. Contrary to the previous answer, the time required to actually replace all 8 spark plugs on the 4.6 litre engine is 60 minutes. You'll need a univeral for your wrench to get the ones in the back.