Hello, I recently have had a problem with my 2005 prius in which the check engine light came on and there has been a lot of shuddering upon acceleration. I took it to a mechanic who diagnosed the problem as the ignition coils. Do you really need to replace all 4? Also, has anyone replaced these coils on there own? How do you do it? From what I have been reading they sit right on top of the spark plugs so it seems like I could do the fix myself. Any help is appreciated! Thanks!