Help Change of Falcon Camshaft 221

I am new on the page and the forum and it seems very buneo and with people who know and I tell you what I am looking for is something that guides me step by step how to change a camshaft that the one I have has been running for 30 years and the cams 1 and 12 are almost smooth without a doll. I give myself a lot of the mechanical part but never disassemble the bottom (the block) some of you change the camshaft? Could you give me instructions on how to do it? Adjustment, working mode, some guide of how to do it would serve me a lot, thank you very much.