A thorough cleaning of the barrel and cylinder (I like CLP), and very little lube to the front of the yoke, and maybe one drop of CLP down the hammer to the sear where it can be reached when fully cocked, or from underneath (tiny amount!) with the grips off. Get some snap caps, or even some #4 x 7/8" wall anchors, and dry fire it in single and double action. Any sluggishness, slippage, or failure to lock properly might be old lube that has turned to goo. Post back, and we can walk you through opening the side plate and getting major on the cleaning and re-lube.
You "MUST" get some good screwdrivers to open up a gun. Never bung up a screw head with a regular screwdriver. Wheeler makes nice inexpensive sets with the proper hollow-ground bits.