I need 2 plugs for st170 coolant temp sensors.

Also need one for the fog lamp in the bumper. One of the cables snaped off right at the plug so i cant solder it back on but I might go to the local scrappy with a pair of wire cuters

After soldering wires together is heat shrink good enough to keep water/moisture out?

I have seen some cars where the wire has just had insulation tape then the copper turns black and you end up cutting the wire back to expose fresh cable.

Also are 12v soldering irons any good? or am i better off with one of those gas powerd ones ?