2000 silverado heater core replacement instructions

I have a 2000 Silverado P/U and I need to replace the heater core. I need to know how to replace it. How hard it is and if someone out there has any intructions on how to do it. I also have 1999 F150 and someone out there had the step-by-step instructions on how to do it. I still have them on my e-mail if anyone needs them.