Doverham,
Just my $.02 but I've finally come around to where I prefer double triggers on my shotguns after paying extra $$ for the privilege of having single triggers on my guns for years.
That said, I still own & shoot guns with single triggers & if I found a gun I really liked in all respects except for a "good" single trigger such as a Miller I surely would not let that keep me from owning it & using it with the single trigger. I have shot several guns with Millers & the triggers are excellent once you get past the look of the trigger with "MILLER" stamped on it.
I'm on the same page with Brittany Man.
Converting it back to double triggers is not an impossible task. In addition to the obviously needed triggers, the trigger plate has to be restored by welding up the trigger plate to a 2 slot arrangement as well as possibly adding the trigger fulcrums for the hinge pins of the triggers. Then like Bill said, the sears need to be straightened and maybe built up depending on how much metal might have been removed. If the trigger guard is too small, that's another issue.
You gotta want double triggers on this particular gun pretty badly to either do this yourself or pay to have it done. I'm guessing you're gonna run into costs exceeding what it costs to put in a Miller trigger today, if a reputable gunsmith does the work.
