99% of the time I do not go for the extended warranty but I just got a refurbed D7100 and got a extended warranty for only 35.00. I think 75.00 is not much for a little extra piece of mind as long as you trust the seller.
I have used 3rd party grips on Canon Sony Nikon of various make such as Meike, Zeikos, some with no name and my current Newer for D7100. All worked as they should and my reason is why spend over $200 for a grip that sometimes I will take off.