My pump started leaking today. Sprays out from under the red cover that bolts to the top with 4 allen bolts. I presume its the diaphragm. Should I buy the regular rebuild kit or the one with the teflon diaphragm? I spray pre-emergent's like gallery, barricade and pendulum. Also should I/ do I need to change the oil? How much air psi do I put in? Any help appreciated. I bought the rig used and have no idea when it was or ever rebuilt before.