Guest: Did you say that your 649 is a stainless version of the concealed hammer Airweight Bodyguard Model 38? If so, a trigger job is pretty easy to do, whether the pistol is stainless steel or aluminum.
First thing you need to do is get a set of Wolfe Springs - they come in kits for the S&W J-frames, and are really easy to change. You might also wish to take an Arkansas stone to any of the parts, like the rebound bar and the hammer strut, to smooth out any rough edges or burrs. And the same thing for any places on the frame where those parts may ride. A good coating of engine oil helps lubricate the mechanism after you've finished. You may also want to stone off any grooves on the trigger or any sharp edges or tips, and look into a pair of grips that fit your hand better.
Most trigger jobs on S&Ws are completed using just new springs. If you add an Arkansas stone to that equation the job comes out much smoother.
Just my 2 cents worth. Mikey.