This one got lost. Sorry about the long response time but I've had computer problems. I went through this recently myself.
The 4x2 Sport Trac has the same wheel bearing layout as most American cars of the past 40 years, with a pair of roller bearings, a seal, a no-spin washer, a nut, and a locking nut cover that will accept a cotter pin. Most of the time the only thing that will need replacing is the cotter pin, unless one of the wheels bearings is bad.
The standard method is to install the inner wheel bearing and seal in the rotor, install the rotor on the spindle, insert the outer wheel bearing, slip the no-spin washer on, and then turn the nut on until just snug. I normally use a pair of "channel-lock" style pliers to tighten the nut, but you can also use a wrench. Tighten the nut to about 30-40 foot lbs while turning the rotor to seat the bearings. Then loosen the nut to remove the pre-load, then re-tighten to about 12-20 in-lbs. I normally just use a "just snug by feel" method, where you tighten the nut to snug, loosen it, tighten it again to snug, and work it back and forth a couple of times, to get that "just snug" feel, but you may prefer a torque wrench. Slip the sheet metal lock on, and insert a cotter pin. If one of the spaces between the tabs on the lock don't line up with the cotter pin hole, pull it back off and turn it to a new position, and then re-install it. If the lock is a little loose on the nut, pull it off and squish it slightly with channel locks to make it snug on the nut.
Be sure and pack the bearings with Ford approved grease, and use a new seal. Work the grease up in between the rollers, or use a bearing packer. If the bearings show any signs of discoloration or if there are any flakes of chrome in the old grease, replace the bearings.
