Bill,hello, is not so much a trigger job as someone did a job on your trigger as is sounds here. it could be the hammer or trigger or a combo of both. if said gunsmith took some material off the trigger`s sear hook/engage surface, making it rounded or short, it can slip off. or, it can be the hammer notch is hardly a notch anymore. took it from a 90 degree hook and turned into a rounded radius. its for sure unsafe as is. you would have to look very close at both. first check in the gun with main spring backed off or removed, with side plate off. you will be able to see how the two parts work togather. next remove both parts and look at the engage surface of both.a magnifier glass helps. you may be able to see what part is at fault.
if your not familiar with taking it apart or have never been inside a smith DA revolver, your better off finding a real gunsmith to check it over and tell you what it needs. as to cost, it depends on what parts are needed or work that could be done to save parts you have. if you know someone who has any extra K frame hammers or k/L/N triggers you may be best off to just try each or both and then see how it works. if that does it, then a part or parts change would most likely be cheaper then gunsmith work to your parts. just my 2 cents. Phil