I've been stripping the head and cleaning all but the metal parts. There are still parts that won't budge; the needle and slide plates. The hand wheel turns beautifully and the feed dogs move so that's a bonus!
One overnight soak in PB Blaster has had no effect so I'm off to give it another good spray.
Glenn has been kind enough to offer lots of help with my questions. Thanks, Glenn. You're a super star!!!