Hey there I just recently started having freezing issues with my Xbox, it would freeze after 5 min or so of being powered on. I'm sure i found the root of the issue when i pulled off the heatsink to find the processor swimming in thermal paste, and some even managed to squeeze out onto the motherboard and onto some transistors. I have cleaned off the old thermal paste, but now I'm wondering if i need to reheat my motherboard for the reflow technique, or since i didnt have RROD, is the reflow even necessary?

You don't have the right equipment to do it properly, so don't do it. Its a technique with limited success to be used only when there isn't anything else that can be done.

Most thermal compound isn't very conductive so chances are that it may not have done any damage.

Well the thing is that the paste seems like it was squeezed out by the heat sinks, there was a lot of paste surrounding the chip but, hardly if any on top of the chip. I've known people personally to be sucessful in this technique so when done properly i believe it can work. Besides the warranty was up a long time ago so I dont have anything to lose here.