First of all I would like to thank all the people involved on Xbox-scene, Llamma and other forums who have made this repair possible.
Disclaimer: Do not use this method if you have the warranty. Use this method as your last resort.
What is RRoD?
Basically, RRoD (Red Ring of Death) is a name given to Microsoft?s 3 Red light error and is a caused by cheap manufacturing.
How do you find out the reason causing RRoD on your Xbox 360?

Hold the Sync button and press the Eject button 4 times. You?ll find different number of quadrants of red lights illuminating. Using this you can make a code out of it. Here is the legend.
All four lights illuminate = 0
One Light = 1
Two Lights = 2
Three Lights = 3
Fixes as per the Codes:
1) Part 1
1RROD E73; E74;
2RROD 0011; 0012;
3RROD 0002; 0020; 0021; 0022; 0023; 0101; 0102; 0103; 0110; 0203
These errors can be fixed by X-Clamp replacement method. Click here for the tutorial.
2) Part 2
3RROD 0001, 0002
Click here for the tutorial.
After your fix, you can try the 12 Volt cooling mod. This ensure longer life of your fix.

I still think reballing, or at least properly reflowing The BGA (Ball Grid Array) components is one of the best ways to go about it. I pick up lead .6mm solder balls to do my dirty work... Take a crapped out 360 to practice on... I will post a video Tut soon, but you can google videos on it if you wanna try it without all the fancy equipment. I have never done a 12V cooling mod, but I have a unit that overheats in about ten minutes, and the fan speed never increases, I'm guessing this would be a nice way to go with that one.

IMO reballing is HARD work.....and you should have some experience to do it.

Does reballing CPU and GPU fix majority of RRoD? Good success rate?

Yes, only reballing is the only good way to fix RRODs. If you only reflowed chips then RROD will back soon, but after reballing it never come back (RROD related to reballed chip). I tried reflow, but on 24 hours the problem is back, but after reball it work for at least one year (checked)

how hard is it, any sort of specialist equipment needed for this, id love to see a tut for this.

Reballing is very hard to do and does need expensive and specialized equipment.

What would be the cheapest equipment I could buy to to reball the chips?

RROD is in almost all cases a cold solder joint under the gpu caused by flexing of the mobo,uneven standoffs,leadfree solder and heat.Usually a good,even reflow with flux fixes 90% of rrod for a good while,specially if a hybrid fix is applied afterwards to keep even pressure on the gpu and keep the mobo flat.A fanmod to keep it cooler and prevent flexing increases longevity as well.Most of them run from 6 Month if you`re unlucky to another 1-3years.I fix Xbox360s every day for a living
A re-ball lasts longer because the leadfree solder is replaced with better,more flexible and less porous leaded solder.
Its a hell of a job though to replace the ~1000 0.6mm diameter solderballs,you`ll need a good rework station,a reballing jig,boardholder,flux... and (much) more than one Scrapbox

RROD is in almost all cases a cold solder joint under the gpu caused by flexing of the mobo,uneven standoffs,leadfree solder and heat.Usually a good,even reflow with flux fixes 90% of rrod for a good while,specially if a hybrid fix is applied afterwards to keep even pressure on the gpu and keep the mobo flat.A fanmod to keep it cooler and prevent flexing increases longevity as well.Most of them run from 6 Month if you`re unlucky to another 1-3years.I fix Xbox360s every day for a living
A re-ball lasts longer because the leadfree solder is replaced with better,more flexible and less porous leaded solder.
Its a hell of a job though to replace the ~1000 0.6mm diameter solderballs,you`ll need a good rework station,a reballing jig,boardholder,flux... and (much) more than one Scrapbox

mod please delete sorry didnt mean to doublepost