I have used my John Deere Z225 several times this year. It was purchased in 2007. This past week I started it and started mowing. I got 30 feet out and then it died. Wouldn't restart well. I had just place new gas in the previous mow. I checked the oil. It was milky and smelled of gas. I replaced the gas cap and emptied the gas, refilled with new gas and changed the oil. When I restarted the engine it was emitting black smoke and seemed to be "missing" as it was running. When I tried to move the mower with the zero turn radius arms it had very little power and was losing power. When engaging the PTO the engine almost stopped but did kick it on to a very low speed. I removed the carb to see if the solenoid or float was the problem. There is a port on the back side (side facing the engine) with a rubber tube carrying up into the engine somewhere. Inside this tube is a slimy foamy white coffee colored fluid. Where the intake manifold enters into the engine/valve area there is a lot of sticky black residue. Included is a picture of looking into where the manifold was removed into engine. Should I replace the carb and the add a cleaner to the system or does it need to be taken into a shop?