I was wanting to replace my valves but cant afford the shops to do it. can it be done my self? I have the factory manule and read about preheating it and poping out the valve guieds and replaceing them but is this something i could do right? I dont have any exsperiances with valves other than seting them but I do have some motor knowledge just dont know if i can do this my self. Anyone else done this are left it up for shop?