I'm glad you chose the replacement. I don't think that repair is exactly something they can follow step by step by the book (as in swapping out the struts). They will have to de-weld body panels and other parts for removal to get to that piece. As others have said, even after it is fixed, can you be sure it will hold up in an accident an have the same, pre-repair structural strength?
My feeling on extended warranties are they are money makers for the dealer they try and sell you during financing (along with Teflon coating and window etching). I had the super-duper gold plated Nissan extended warranty on my Xterra and when it had a cooling issue, the problem was one of the small coolant hoses you can't even see (not the two big ones going into the radiator) they wouldn't cover it under warranty saying it was wear and tear. $10 part and $600 labor later (deep in the engine somewhere). I came to the conclusion that I paid for a warranty that was useless. If there was a major problem with a car (ring lands etc) it will usually present itself within the first 36k miles.
In the meantime, drive the piss out of the car you have, maybe a few track days... and enjoy your brand new car knowing you've already taken one to its limits!