I just bought a 07 Jeep Commander 4.7 4wd that hit 72k and I did the maintenance out of the manual which was rotate tires, engine oil, and inspect the brake system. I just hit 75k in a matter of 10 days going from CA to TX and then back to AZ and the manual says for engine oil, air filter, axles and drive belt. I am unsure of what to do for the axles and Im sure I just inspect the drive belt for the normal wear. Is it necessary to do anything to the drive belt or axles? I also want to change the spark plugs and I have read mixed reviews on the E3's, any thoughts? Thank you.