The 52 is a fantastic gun and the -2 variation is a good one. Some pictures would help identify whats going on with your trigger. You can try Numrich or other online sources for a replacement or try to find a used trigger on eBay or other auction sites. The model was dropped from production in 1993 so the factory probably does not have any, but you could call and check.
Based on serial number, it looks like your gun was made around 1979.
.38 Mid Range means the gun only fires 148 grain .38 Special Wadcutters (see picture below). It's a target gun designed for target ammo.
Here's my mid 1970s 52-2 in the original box along with the ammo it's designed for.