If you get the YLoD the system is basically screwed, and any fixes (even reballing in my opinion) are only temporary solutions.
Most reball repairs only reball a specific area, like the GPU and fewer reball the CPU. It is possible the issue can happen on any of the solder points on the motherboard so other aras can fail even if the reball on the GPU/CPU holds up.
YLoD is caused by overheating, and poor quality solder. The overheating could have (and most likely) caused degradation of the chips, significantly reducing the life of those chips.
Like the post above me, reballing as well as reflowing can also increase the problem because you have to subject the motherboard and it's components to even more heat for those procedures to be successful, it may get the system running temporarily, but you won't notice the damage until it fails again later on.
You're better off getting it running, sell it to a pawn shop and buy a new PS3 if you need PS3 compatibility.
I spent money getting my PS3 reballed and it failed again a few months later, so I'm just trying to save you some cash.