Keep an accurate log of each step, work from the bottom of the playfield up. I number my steps and work in sections. Take pictures constantly. I use ice cube trays for all screws and washers etc. I number each slot in the tray and in my log note what I did. I lay all plastics on a table in approximate relation to playfield.
Example:
Step one. Removed ball guides to flippers, six screws, 2 longest screws were at the top of the guides.
Then I put all six screws in the first ice cube tray compartment.
When you put everything back work in REVERSE order.