oil change

I get the gen serviced and engine once per year at a Cummins Coach Care facility. All filters including fuel, oil, lube job and bumper to bumper inspection run me 638.00. Last year the tech found a bolt had vibrated out of the engine a/c mount. While it had not gave me any indications of trouble it would not have made it another year with out causing some woes on the road. This includes coolant check as well. I do all my other oil, fuel changes myself on my other vehicles including the tractors but accessing all the zerk fittings, and getting to all the filters on the dp are a bit challenging and unsafe. I just prefer having an expert to do it.