I have an old wingmaster thats about 30-40 y/o and been through hell. I am going to send it off to bell and carlson after I get a thumbhole stock and new forearms for it and get it camoed. Now I was wondering if a trigger group from an express or newer wingmaster would work for it. or is there any parts that won't interchange?

Not sure on that one, although my gut tells me they are interchangeable.
I'd have to call Remington for sure.