I've done that trigger job on my Neos. You absolutely need a screwdriver bit to fit that screw. It is a gunsmith cut flat bladed screwdriver.
I have a cheap-o multi-tip gunsmith screwdriver set but the bit I needed to fit the screw head wouldn't fit into the opening on the sear housing. I had to file the body of that bit to clear it.
You need a near perfect fit of screw driver to screw in this situation to transfer all the torque properly. When you put that screw back in, just use blue Loctite after you're satisfied with the sear spring you install.
One important thing about that hexidismal trigger job. I found that you don't need to polish every little surface to get improvement. The one thing you absolutely must "polish" is the inside of the sear plunger as well as the outside of the sear plunger. The inside is cut really rough and contributes to most of the gritty trigger. I had to use a tiny bit of rolled up emery cloth and spin it in the bore of the sear spring plunger.