Truck Repair: Preventative Maintenance, air filter element, rear brake drums

Question
I have 1 1992 Dodge D250 4x2 truck w/cummins 5.9 engine.  Besides oil, air filter, antifreeze, what other PM kind of stuff could I/should I be doing? truck has 113,000, no problems with the engine.  Have owned it for 3.5yrs and haven't done anything else (well, new shocks/tires).  Also, how do you get the rear brake drums off? I tried, but they wont budge.  Hammer? does the axle half shaft have to come out? thank you...

Answer
The number one killer on the engine in the Dodge is the air filter.Some people try to save a few bucks on the air filter element & the cheapo filter doesnt seal off & the engine gets dusted(Dirt gets into the clean air side of engine & wears out the turbo,rings, & head causing lots of blow-by & oil consumption).Also dont forget about the fuel filter.The valves probably need adjusting if you have not done it in that milage.The drum thing now,if it has a floating axle(small bolts or nuts holding axle in rear end),then the axle might have to come out.If yo dont have that set up then probably need to hit it a few time on the axle to free it due to some rust & corrosion.