If you don't get a good response here, try the rimfirecentral.com Winchester forum. There is a fellow there, user name "Seewin", who provided me with good information when I was having trouble with my 52D micro-motion trigger.
I can't help you with who works on them as I do my own work. I think there is someone in Texas I've heard about but the name escapes me at the moment. Hopefully someone will know who that is... FredJ?
What is the problem?, gummed up, out of adjustment, or physically broken?
First two are often easily fixed, if broken, that's a bit more difficult...
Happy Shooting,
Mitch & Shadow...