I recently bought a 93 and went through the usual maintenence items.
Plugs-Wires
Oil & Filter
air and fuel filter
PCV valve
cleaned throttle body and MAF sensor
cleaned IAC valve
flush and refilled power steering
flushed out old brake fluid
front axle, transfer case, rearend fluid change
tranny fliud (not done yet, it got too cold!)
grease and/or lube all hinges etc
new radiator cap (had a new radiator)
checked brakes and lubed slide pins
Granted I bought a fairly high mileage Exp, yours may not need all of the above. Use your best judgement, if your not sure, replace it. Good maintanence is cheap insurance as far as I'm concerned. If its a 94 or before, check radius arm bushings.
On cleaning the engine I use engine degreaser if its real dirty and Simple Green or similar if not too bad. When the engine dries off I use clear silicone spray on everything.It protects, looks great, and doesn't leave a greasy residue.
Hope it helps, and enjoy the Explorer, I sure love mine!!
Chris