One of my first clean up was a 1928 99. So dirty, rusty and stuck I thought well I can't hurt it. So with triflow and sewing machine oil and a lot of work. He sews just fine. I call him Little Giant because despite being so small and pin scared neglected he still sews and has obviously done lots of work.
So go for it. The biggest problem I had with it was removing the bobbin holder, which was crammed full of felt like lint and dirt. The manual helped me a lot and so did this board. Thanks everyone.