Does any one have a simplified maintenance schedule for the Walker? The manuel is very detailed and when I give it to my crews they do not understand... (it takes me 20 min. just to read through it!) Also.. any one know where to purchace air filters and prefilters for this machine online? No one seems to have them. IM talking about the pre filter before it gets to the engine(has an outer and an inner filter) My dealer is getting me for like $40 bucks and we change them monthly.