"Arthur",
Are you sure it's the pickup shoes? These engines often begin squealing because the armature needs oil at the fiber brush plate. This end of the armature need lubrication very frequently as the fiber tends to absorb oil quickly. Do both ends while you're at it, but it's the fiber end that is usually the culprit. I'd try that first if you haven't already.
But "Don't panic" and keep that towel handy. (Sorry - couldn't resist! )
Jim