If you got the box with your used pistol, check the SKU number on the S&W website to see if you do, in fact, have a MA trigger. If you don't have the box, S&W customer service might be able to back check to determine the SKU and the appropriate trigger weight.
Having started to work with revolvers again, the length of the trigger stroke (on any handgun) and the quality (smooth or rock garden) is much more a problem for most than the weight.
If it does have the 10 lb trigger mechanism and you aren't required to have that, check with S&W to see if they'll exchange the parts for non-compliant parts. I expect S&W would be willing to at least take a look at it under their warranty/customer service program. If not, I'm sure some competent local gun smith can do the parts change at moderate cost. Emphasis on the "competent".