Well, if apple is picky, they can blame it on the ram installation since you (the owner) is not a certified technician. Even though RAM in a MBP is user replaceable, apple still suggest that it should be "professionally installed". Being said, lots of things can happen during RAM installation if it is not done properly (e.g.: Did you unplug the machine installation? Did you shut it down the macbook properly before removing the cover? Did you unplug the battery before you install RAM? Did you ground yourself (anti-static wrist band / ma) before you touch any components include your new RAM?).
Like someone said already, I would bring the machine to stock configuration before I send it in for repairs. If the new part is causing issues, the user would have most likely caught it the minute it was installed. If everything works. then you are all good.