Most important maintenance with the 2001-05 Sport Trac's are the transmission and timing chain guides. Check the tranny fluid for a burnt smell and dark color. If so, a pan drop and filter change is probably the best thing to do. Regarding timing chain tensioners, it's not if, but when they let go. Some have failed below 70k, a few other are approaching 300k without noise or issues. Routine oil and filter changes are critically important. The factory spark plug interval is 100k, but that's approaching 15 years if they're original.