No push off. Great! At least we know that no one has monkeyed with the hammer/trigger and the pic verifies that you do not have a roller conversion.
The gun looks pretty good from here. Not much apparent wear. Little evidence of hammer dragging on the side plate (can't see the other side). The cylinder notches look good and the inside looks very clean. Doesn't appear to have been shot to pieces.
As noted, a new mainspring is cheap. While you're doing all this, measure the actual firing pin protrusion, head space, end shake, and cylinder to barrel gap. They are all related and end shake caused from wear or improper fitting can affect headspace and cylinder to barrel gap. Combined with inadequate firing pin protrusion and/or a weak mainspring, you will have a pretty paperweight. Firing pins are seldom short, but it is worth checking. More common to find an end shake/cylinder to barrel gap problem. Does your cylinder latch into place easily when closing (yoke straight)?
As for polishing, without knowing your sense of when "enough is enough" and what not to touch, I advise caution. I won't say don't. Just proceed with caution. Resist any urges to "clean up" the machining marks on the single action hammer hooks (yeah, the do sometimes look rough up close) or to stone the single action sear surface on the trigger. That's a quick way to generate push off problems and destroy the single action trigger.