3d printer heads like the one you link to typically have a thermistor that is only rated to slightly above 300C. You would need to find a higher temp thermistor or use a thermocouple.
The nozzle opening (typically 0.4mm or so) is probably much too narrow and you'd want to find a nozzle with a larger opening. Or perhaps drill out the 0.4mm hole to something larger.
Extrusion heads like that are designed to maximize heat in the central block - not at the nozzle tip. So you'll actually need to run it slightly hotter than a soldering iron would be.
You will have a difficult time seeing the workpiece behind the heating block / cartridge heater. Also, the thick heater wires typically protrude from the side, making it even more difficult to see around.
Lastly, the nozzle will come up to working temperature FAR more slowly than a real soldering iron would. A soldering iron will only take a few seconds to reach reflow temp. An extrusion nozzle will take a few minutes unless you power it VERY aggressively, which will make it very hard to control the overshoot.