Take it apart piece by piece, take pictures so you know how everything fits back together. I do all the prep work as I take it apart. This allows me to order the parts as I see things that need replacing. Keep a note book of ordered parts, compare the new to old to check that the new is correct.I tape the new and old together , ziplock bags , sacks and small boxes work well. Lable them for easy identification when reassembly. This makes many small jobs. Keep the log up to date and make notes for future activity. Do not throw anything away until the reassembly is complete.
Eat the elephant one bite at a time, they are hard to swallow whole!
