Depends how brave you are. I replaced mine myself, but did so accepting the risk that if I borked it then I would be looking at a) loss of data, b) permanently damaged macbook. As cost of replacing macbook is circa 2K I took a deep breath, calmed down, read a few how to guides online, and cracked on with it.
I maximised the amount of RAM at the same time. 7 Year Old macbook is now faster than I ever remember it (thanks to SSD) and definitely more stable than of late (I can now run a couple of virtual machines without hassle) thanks to the increased RAM.
If you want the peace of mind of having a professional do it, then you pay what they charge. Ring round and see who you like dealing with would be my advice.