Re: 2004 Explorer question
The bearings on my AWD Durango are sealed as well, and come as a complete assembly. It's a PITA to replace. The last one (right front wheel) I had to heat to get the 32mm nut off as it was on there solid. Took about two hours, remove the disc brake and caliper, pull the axle shaft, pull the old bearing and replace with new then reinstall.
Sometimes (it's too late for you now), it's best to check online for parts as you can often luck out. I pick up Timken bearings online (half price of what the dealer charges for their imported Chinese stuff) and have had great luck with them over the years. I tow regularly and my last front set of bearings lasted 102K miles.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!