So with these, pretty much any chips we can get for them will not last very long. Most supposed "New" AMD chipsets are either rejects or reballed garbage, so while soldering a new chip to the board is not a problem, getting a good chip that can last and be reliable is.
Sellers on ebay that claim to replace the GPUs are more often than not heating the chip up with a heatgun. Heat will make the chip work for a short amount of time.
Others will claim to reball the GPU. This again will only last for a short amount of time. The issue is not the solder balls. It's the bumps in the die itself. The heat involved in reballing will do the same thing that a $30 heatgun from home depot will do.
These machines are nice as far as serviceability... You can replace the battery with easy contrary to the 2012 and up Retina. If you have a 15 inch, I'd say get a 2012 board for it. These use a different chip and will work. You may need to do a slight modification to the LCD cable to get it to fit in the new board.
The board you want is a 820-3330. It uses a completely different GPU and will last you a good while into the foreseeable future.