Hey, I've overfilled too, at both ends - I think enough slopped out that I got lucky with the drag thing. Before going to the trouble of rebuilding, I'd check the caliper guide rods for grease - I wouldn't be surprised if it's burnt to a crisp, leaving 'dead-grease glue' on the rods, As long as the caliper & piston move freely and don't leak, you might be OK. The new pads will likely be thicker, and almost always I've had to slide the caliper way apart and push the piston(s) farther into the body before the new pads would go on. After that, a couple of strong brake applications and I've always ended up with zero drag after a pad change.