Dan,
I missed that part of your meaning. I'll be into the gears and springs and timing issues when I get into that 538 of my wifes.
It's got one gear that really needs repairing, but since it has other issues like you described I'm going to replace them all, then using the factory service manual I'll start from one end and work through it.
For a novice or someone who doesn't want to mess with these things I wouldn't even suggest a Singer with plastic gears.
Joe