Soldering is probably one of the easier DIY electronic jobs out there. Most hand held "wand" type soldering irons are sufficient, but occasionally you'll find they just don't get hot enough (30w usually) and you may need a 50 or 100w iron. For the circuit board on the EVSE, a 30w iron should be enough. Just make sure you take your time and verify that you don't solder two adjacent terminals. If this is your first time doing this job, I'd suggest taking high res close up shots and comparing the before and after images of everything you solder to make sure it's right and nothing got connected to the replacement solder points that shouldn't have.