It most likely would be risky as you don't know the quality of the cells in the battery pack. For example, you could buy cells from Samsung and know they would be of great quality, but you could also buy a nice cheap pack of cells on Ebay, but you have no idea on their quality, lifespan and true capacity. What you could do instead is find a dissassembly video and have a go at replacing them yourself. That way you can replace the current ones with genuine, good quality cells.
[link|https://www.youtube.com/watch?v=Nbc4FJrOiXI|Try take a look at this.|new_window=true]