Firstly, C4 is a capacitor, not a resistor.
Secondly, the iron won't melt the plastic, how do you think the capacitor got there in the first place? Having said that, I would recommend to use thin tip low-power iron for electronics (15-20W), not the 100W+ industrial type.
Beware, you'll need 3 hands to successfully solder the part, one hand to hold the capacitor in place, another one to use the iron and the third one to feed the iron with the thin (0.3mm~0.5mm recommended) solder. It might be a good idea to use a solder wick on the capacitor pads to remove leftover solder before soldering it back (or not, if you feel adventurous =)