When we instaled our seal it was hard to shut until it had sat in the sun for a while. We also glued ours in which helps seal it from moisture. We used the softseal as well. We had to use a small tipped screw driver to poke the edge of the seal all the way down to fit in the channel.

Those after market gas door springs work fine. We replaced ours. You need to drive out the pin with a small punch. You could also use a piece of steel wire the same size in diameter. Nothing smaller though since that pin is split on one side and you will just flare it out using to small of a punch.