I'm far from being an expert, but I have done the swap at least 6 times. KILLR-V's car has no squeaks or creaks from the suspension and they've been installed for close to 6 weeks I think and he has a 30+ minute commute everyday to work, do he is putting some miles on it.
As for the piece not turning, they over tightened it... it doesn't need to be that tight. You have the electrical connection to the long electrical conductor (basically looks like a long nut with a receptacle on top), and then the nut under that. You have to get that electrical conductor off to gain access to the nut. It should spin right off. Under that you will see the threads from the shock top and the nut holding it together.
I would definitely trim the front spring. Todd's rear was lower until we trimmed 1/4 coil from front spring. His measurements are now 26 5/8 front, and 27 1/8 rear for a 1/2 rake which is about perfect.