Dang. Sorry to leave you hanging. I need to follow up on my threads more often.
With your experience in mind, you need to seek out someone to do it for you, wombatman. Yeah, your machine will be down for a few days, but that's better than it getting cooked.
If you want to gain some experience, try some basic kits online. Maybe something like this Dual Dice Kit from Jameco would be a good place to start. It has some surface mount stuff and some basic resistors, etc.
Dice Kit
You will also need a solder iron and some really tiny tips, plus some solder. Try a basic Weller WLC100 iron from Mouser
WLC100
I imagine it will be around $50 for the solder station, $15 for the kit, maybe $5 for the tips and another $5 for the solder.
You will also need to grab a multimeter to check your work before you fire up the board. That's another $25-$250...
Now, it's all gettin a bit pricey, right? To be honest, I'm trying to steer you away form doing this. Unless you are willing to risk the motherboard or have a spare, I really would rather have you pay someone $25 bucks to have an experienced person do it. After re-reading your post that you will generate extra heat, why not just get a better cooling system and skip this micro-soldering part.
Not trying to wimp out on ya, I just think this mod is technically pretty challenging.