will a 12 watt soldering pencil do the job of soldering a mod chip in place?

It should work, but you might have problems melting solder in some spots on the board with a larger surface area, like the ground plane.

If you already have it and can't return it, then give it a shot. Otherwise, you are best off buying a $10 dual-wattage iron from Radio Shack (15-30 watt).

The wattage is low. The installs can easily be done with quite a high wattage iron with a small tip. Damage is usually only done by applying the soldering iron to the print or connection points for too long. I would get a slightly higher wattage and invest in a good tip for the it.

ok,thanks.

You could get away with a 20/40 watt soldering station from RadioShack as well (the higher setting is good for desoldering braid use). As Chancer stated, damage to traces and soldering points are done by applying heat for too long in a spot.

My setup is a 15 watt iron from RadioShack for soldering, and a choice between 15 watt iron + desoldering braid or 45 watt desoldering iron (which is useless in tight or delicate areas, but good for removing stuff like pin headers and other items with legs (eg, cylindrical caps)). I ended up getting a soldering stand w/sponge, but that's all included with the 20/40 watt station.

Go to your local RadioShack and buy a 15w soldering iron or a 15/30w.