I don't rely on memory. In my case that would be a terrible mistake.
Take plenty of pictures as you go (and post them here)
. Bag sub-assemblies together and label them when you can.
The more you can keep sub-assemblies together as you take things apart, the easier it will be to put it all back together. I've rebuilt several wood working machines and it's worked pretty well for me. I have yet to completely disassemble a sewing machine though.
Alcohol works well for dissolving old sewing machine oil and is less dangerous than many other solvents. You just can't get it around any shellac you want to keep. Rubbing alcohol may be cheaper than denatured alcohol and works well.
Rodney