The guides are a interference fit in the head casting. The head will have to be heated in an oven to a uniform temp. The guides are usually pressed in to the casting. This is best left to a machine shop with the correct equipment. Generally not a DYI type of task..
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.