I kept getting the rainbow circle slowing my computer down no matter whether I was in a document or online. I was getting very frustrated - to say the least! Called Apple several times, but couldn't resolve the problem. They finally recommended that I purchase more RAM, but because my Mac is an older model, they did not sell RAM for my computer. The rep gave me Fixit's name -- end of story.
I watched the video on youtube on how to install the chip and it was so clear and straight forward that being a non-geek person, I had no problems at all.
If a 75 year old non-geek can do it, anyone can. My geek grandson was very proud of me!