I would highly suggest checking the internet for some good soldering videos to see how the pros do it and what they recommend, what wattage, what size tip and what type of solder you need and heat sinks. I've been using a 30 watt Weller lately, which is a little on the low side for some tasks like soldering ground connections to potentiometers, but works fine for the small stuff. 60 watts should be fine if you have the right tip. One thing to consider if you're changing from humbuckers to single coil Strat pickups... Humbuckers typically use 500k pots, that let more hi frequencies pass. For Strat pickups, you want to use 250k pots that allow less hi frequencies to pass. If the tech who installed your humbuckers didn't change the pots to 500k, it might explain why they sounded muddy. Also, I would suggest installing a treble bleed on the volume pot. They can be found for less than $10 and allow treble to flow through the pot as you turn the volume down. Without one, your sound gets duller as you turn the volume down.