Need to replace U-joints in my 2000 Yukon. I understand that they are held in place by injected plastic that must be heated or burned out before they can be disassembled/replaced. Is this true? How does one go about doing this and can you damage the driveshaft by overheating? How do you know when you're done cooking the plastic out? I have the means to heat from propane torch to oxy-acetylene rose bud torch tips.