Quoted from NicoVolta:

Right on. "Total rebuild" is the basis of what I teach at VECTOR. Every-everything taken apart, cleaned, adjusted, made perfect, and then upgraded with the optional "better than new" tweaks.
EM's pretty much always need to be rebuilt after 40+ years of hard use and neglect. Just have to do the process... no shortcuts.
The best part is how EM maintenance changes your perspective. From wanting to "hurry up and play" to slowing down and "understanding the whole machine". It really is a Zen process and why many of us eventually get as much joy restoring the machines as playing them.