Bundle Me cover for carseat???

I wanted to install the bundle me lite car seat cover since we are going out tonight to a block party and it has been pretty cool out at night.
If you go to install it in your infant car seat
1- do you need to not use the head insert that came with the car seat anymore - DD still needs this (she is almost 7 weeks old)
2- do you have to remove the original padding that came with the infant car seat or does the bundle me go over it
3- how the hell do you remove the straps to thread them through the bundle me ??