Where in SoCal are you located? Duncan's Gunworks in San Marcos (San Diego County) has a good smith, but I don't know how close that is for you. It seems sometimes like most of the good smiths have gone out of business or left the state. They are sure getting hard to find.
Another option may be to replace the trigger yourself if you aren't comfortable with polishing the sear. WWG makes a drop in Happy Trigger that is simply outstanding although it's on the expensive side, around $90 from Brownells. That might be more than a smith would charge, but it's something you can do yourself if you have even minimal dexterity with tools. It might just be the best upgrade you could possibly make to a Marlin though. Lightening up the hammer spring or replacing it with a lighter one will also help.
